Welcome to bargain Britain: retailers are offering discounts of up to 75% to kick-start consumer spending as the Christmas shopping season gathers pace.

Shoppers over the age of 16 stand to save £5.5 billion — an average of £115 each — this festive season by taking advantage of the unprecedented number of high street and online discounts, according to the Association of Accounting Technicians (AAT).

Tom Kelman at the AAT said: “The range and extent of discounts we’re seeing this year, along with the reduction in Vat, make this one of the best years for Christmas shopping.”

Follow our step-by-step guide to the best discounts on your festive spending.

GIFT SHOPPING

There are a growing number of short-term guerrilla sales on the high street.

You can also save money on the high street with vouchers printable at Vouchercodes.co.uk/printable-vouchers.html. Today, you can save 20% at Warehouse, Habitat, House of Fraser, and Muji using the vouchers. Other top deals include 30% off at Monsoon and up to 40% off Pringle.

Not all discounts are valid if there is already an in-store discount, though some retailers, including House of Fraser, will let you take advantage of both.

If you can’t face the high street during the sales blitz, you can still make savings using online discount codes. Other voucher code websites include Myvouchercodes.co.uk and Latestdiscountvouchers.co.uk.

The biggest savings can be made if you combine these with cashback deals via sites such as Cashbackkings.com.

Simply log on to the cashback website and click on “shopping” to see the deals available.

For example, if you wanted to buy a Samsung home cinema system from Currys costing £979, you could get a 10% discount, or £97, using the code “CINEMA10” available from Vouchercodes.co.uk.

You can get another 3.5% cashback if you click to the Currys’ site through the Cashbackkings’ site, giving another £30 off — a total saving of £127.

Your cashback account is credited within 14 days of making a purchase and you can transfer this to a nominated current account after two months. Other cashback sites include Quidco.com and Greasypalm.co.uk.

FREEBIES

If you are coming to the end of your mobile-phone contract, you could save hundreds of pounds on your gift shopping by taking advantage of the “freebies” on offer.

Phones4U is offering a 16GB iPod touch, worth £200, for signing up to an 18-month Orange contract costing £30 a month. Carphone Warehouse is offering an 80GB Play Station 3, worth £299, if you sign up to a £30-a-month contract with O2 for 24 months.

Chris Frost of Gadgetstylist.com said: “If you’re already thinking of buying one of these gadgets you could shave hundreds of pounds off your Christmas shopping bills.”

CHRISTMAS LUNCH

The average cost of Christmas lunch is about £70, according to supermarket comparison website Mysupermarket.com.

The cost has risen slightly from last year. However, supermarket chains are also trying to lure consumers with deals and discounts — and searching for the best prices can knock money off your bill.

Until the end of today, Tesco is offering two litre bottles of Bombay Sapphire gin or Absolut vodka for £25 — a saving of up to £8.90. Sainsbury’s has cut the price on Vintage Cava by half until Christmas and slashed the cost of Dow’s port to £5.99 from £11.99.

Mysupermarket.com compares the price of goods at the main UK supermarkets, including Tesco, Asda, Sainsbury’s and Ocado, and also highlights the top Christmas deals.

Marks & Spencer and Majestic Wines offer 5% cashback if you make a purchase online via Cashbackkings. Quidco gives £5 off your first online order from Tesco, and 3% cashback on its wine.

FAMILY FUN

Many of London’s top shows have dropped their ticket prices. From last week, a £50 “crunch buster” ticket has been available for popular shows in London’s West End, such as The Phantom of the Opera, Oliver!, Les Misérables and Avenue Q. Without the discount, the tickets could be a third more.

Crunchbuster tickets admit a family of two adults and two children, and are available at Crunchbustertickets.com.

If you want to take your family out this weekend, Pizza Express and Zizzi have a two-for-one deal on main meals if you print a voucher from Vouchercodes. Pizza Hut is reducing the cost of all meals until the end of today by 15% as part of its “Vat-free weekend”.

KEEPING IN TOUCH

Calling friends and family abroad or calling home if you have decided to celebrate Christmas outside Britain can be expensive, but there are some deals available to reduce costs.

Lycamobile, which offers Sim cards only, reduces call costs by routing calls over the internet. It is offering customers unlimited texts until January 2 to anywhere in the world.

To take advantage you must sign up to a pay-as-you-go Sim which costs £5, though this is added as credit which can be used to make calls. You have to top this up with another £20 of credit to qualify for the free texts.

Cut the cost of Christmas

Isabella, four, and Imogen, two, expect a bumper Christmas thanks to their parents’ bargain-hunting. Audrey and Colin Woodbridge of Barnstaple, Devon, have saved over £200 using discounts. They netted £50 cashback through Caskbackkings

Gym chains bank on VAT

Shoppers might be enjoying a 2.5 percentage point cut in Vat, but some companies are refusing to pass it on, The Sunday Times has learnt.

Health clubs Bannatyne’s, David Lloyd, Fitness First and Virgin Active are instead pocketing the cut in Vat to 15% from 17.5%, which came into force last Monday.

By doing so, Bannatyne’s and Fitness First alone are set to boost profits by a collective £520,000 a month, based on their current membership numbers and average fees.

David Lloyd and Virgin Active declined to disclose these details.

Daniel Lyons at the accountant Deloitte said: “There’s no obligation for firms to pass on the cut . . . By not doing so they will boost their profits at a time of economic uncertainty.”

Gym members, who can pay as much as £70 a month, or £840 a year, should have benefited from an up to £18 a year reduction.

The health clubs said they would instead abandon price increases planned for next year.