Dating websites are a crowded resource used by about a third of British singles, more than four million people. With scores of options, some with subscriptions of £30plus a month, looking for love online can be a daunting and expensive experience. Experts advise would-be users to research the market and enter with realistic expectations.

Petra Boynton, of University College London and an expert on relationships, says that the sites can be used to chat, meet people and build confidence but should not be regarded as an instant fix. “Use them as just one more place to meet,” she says. “Do not forget hobbies, social groups, friends as matchmakers and social networking sites.”

Dr Boynton adds that little independent evaluation of the sites is available, so common sense and caution are essential. Safe sites should give their contact details and answer queries. As always, it is vital to read any website’s terms and conditions and privacy policy before registering or handing over payment details.

Websites that offer free dating include OKCupid.com. This American offering has a large UK membership – 2,035 straight girls aged 18-28 in London, for instance, or 44 straight men in York. In addition to standard searches, members can take a number of “tests” to find matching personalities. For my research, I took the site’s “how romantic are you?” quiz, scoring 84 per cent and landing 20 possible matches in the capital.

Unfortunately, home-grown free sites are less slick. Options include Freedating.co.uk and Flirtbox.co.uk. Both feature a fair number of suggestive profiles and photographs, hinting that some members are after “casual encounters”.

Shimrit Elisar, author of Everyone’s Guide to Online Dating, says that free sites are worth a shot. “It is best to try the free sites first, but be willing to invest some money if that is what it takes,” she says.

Misleadingly, most pay sites invite visitors to “join free”. This provides a basic membership of limited value. Users can post a profile and photograph, search and view other profiles and send virtual “flirts”. However, the all-important means to make contact is made available only to those who pay to upgrade to a premium deal.

Ms Elisar adds: “If you are hoping to be able to sneakily arrange dates without paying, you will be disappointed. Subscription sites depend on membership money, so have measures in place to stop exactly that.”

The two best-known pay options are DatingDirect.com and Match.com, both of which have millions of active members. Both offer free membership as described, allowing prospective users to view the profiles of possible dates. Premium membership of these sites enables various methods of communication, including a video option at Dating Direct.

Many pay sites offer introductory deals or “guarantees”. Dating Direct, for example, is offering an extra month free for signing up for three or six months, while Match.com pledges to find you someone special within six months or give you six months free. To qualify, users must “respond to or initiate communication with at least five members a month”.

These and other big-name pay sites, such as Friendsreuniteddating.co.uk, have the advantage of numbers, with members in the most isolated areas. If you have faith or lifestyle requirements, however, niche sites, such as JDate.co.uk, for Jewish singles, offer a more targeted service.

One catch on most sites is “uninterrupted membership”, where customers ending one contract are rolled on to further deals until they cancel.

Ms Elisar cautions that few people can keep up with more than one site at a time. “There is no point paying for two unless you have time to be suitably active on both.”

Dedicated dating sites are not the only route to love online. Dr Boynton believes that free social networking sites, such as Facebook and MySpace, offer an alternative, widening social circles and users’ pools of friends.

CASE STUDY: Planning a September wedding

Kamilla Pierzchala's decision to date online paid off within weeks. The 25-year-old, who works in marketing, had one “disastrous” date with a “probable alcoholic” before finding Keith Whatling, a London Transport official. Months later the couple, left, were engaged and they are now planning a church wedding in September.

The couple spent days messaging and chatting on the phone before meeting for a romantic walk. Miss Pierzchala chose DatingDirect.com, which costs £59.94 for six months, on a friend’s recommendation and says that the site offers good value. She adds that two of her friends have also used dating websites, both finding boyfriends. Her mother has had a go, too, “with less successful, or more varied, results”.

Online dating safety guide

A no-brainer, perhaps, but never post personal details, such as your telephone number, on the internet.

Free classifieds sites, such as Craigslist.org and Gumtree.com, list hundreds of personals. These are not actively moderated and attract their share of scammers, plus one-night-stand types.

Scammers sometimes post fake profiles on the less-moderated sites. Be wary of someone who looks too good to be true.

Free dating sites tend to be advertisement-heavy – it is how their owners make money. Read the small print before registering. Your contact details may be sold on to spammers and you may be required to download “spyware” or “adware” that monitors your computer use.

For advice on safety and online dating, visit GetSafeOnline.org, the government website, and Shimrit Elisar’s www.onlinedatingbook.co.uk. Both list precautions for real-world dates, as well as online chat.