All went well. We had no trouble using up the sun lotion. Ditto the booze. Not, however, the traveller’s cheques — they returned home in pristine condition, having proved virtually useless... later, as it turned out, they proved considerably worse than that.

The cheques — American Express, from our local Post Office — were all denominated in euros, to save hassle, but to our chagrin, not one bank in the small towns and villages would take them. The only time we were able to exchange them for cash was at the British-run canal-boat company.

So we were back to plastic. Annoying. We got the cheques to avoid the foreign-exchange surcharges that credit-card companies impose on overseas transactions. In otherwise delightful Capestang, I went to all three of its banks. Two were branches of the huge Crédit Agricole and Caisse d’Epargne, while the third was Banque Dupuy de Parseval, part of the global HSBC empire. Everywhere, I received Gallic shrugs and apologies. Checkmate in three moves.

Summoning up 40-year-old A-level French, I marched on the mairie. How can tourists spend cash they haven’t got, I spluttered. The bored clerk politely suggested I complain to the bureau de tourisme. I tried. And the clerk suggested I try my luck at the post office. Another trot round town in the heat. Another non.

First stop back at home was the Post Office where I’d bought the cheques. It would take them back — at the “buying” rate. A quick calculation revealed that I would lose about £70. I protested to no avail.

Refusing to accept the loss, I took my traveller’s cheques home — I would surely be able to cash them in future in a larger town such as Calais or Paris.

A couple of weeks later, I had a sailing trip lined up from Rye to France. I had a brainwave. Surely the Post Office would swap the cheques for euros. It had already made its profit selling me the damned things in the first place.

Certainly it would. First it would swap the euro traveller’s cheques into sterling, before swapping the proceeds back into euros. All very simple, and all very expensive. I pointed out to the entire queue that the Post Office would now make three lots of foreign-exchange profits at my expense.

I still have my traveller’s cheques. And it took more than three weeks for the Post Office to respond to my complaint. Only one of the organisations that let me down had a convincing, if unsatisfactory, explanation. HSBC said that Banque Dupuy did not accept American Express cheques because it has no commercial agreement with Amex: “Their cheques are not as acceptable as they make out.”

Crédit Agricole insisted it was a mistake — I had been unlucky to encounter a clerk who didn’t know how to change traveller’s cheques. Incroyable. Caisse d’Epargne did not reply, despite several reminders, and the Post Office said: “Rural areas with limited tourist facilities often have lower acceptance. We always advise customers travelling to these locations to take local currency.”

Are we to believe that if we tell a Post Office counter clerk we’re off to rural France, we’ll be advised our traveller’s cheques might not be acceptable? In any case, the Canal du Midi region is not the Sahara — there are three airports serving the UK within an hour’s drive. As for the reference to local currency, these cheques were, of course, denominated in euros.

Worse, the Post Office still refused to give euros for my euro traveller’s cheques. It will not honour the cheques it sells. Why, then, should it be surprised when French banks do the same?

Times recommends

• Bogus websites are conning hundreds out of their holidays
• The complete last minute holiday guide
• Croatia: the flashing blades of Korcula