Pocket Money: Plan ahead for a cheap holiday, I thought. Oh dear...

there's a problem inherent in putting down a deposit for something. When the time comes later to pay the balance, it's hard to remember how much the first chunk was. Well, it might not be hard for you, but it is for a multi-tasking (oh, all right then, pea-brained) person like me.

Last autumn, when we'd haemorrhaged money on a spectacular holiday to South Africa, my bright idea was to plan ahead and save money. In 2008, I thought, we'll stay in the UK and find a charming little cottage somewhere for not much money. I found the ideal place, by the seaside in Wales, with lots of space for the children to run around in, and lots of sofas for me to lie around on. I paid my deposit and filed the plan in my brain under "sorted".

The months rolled by, and Wales is on the horizon. This week, both children finished school and brought home the fraying and ripped remnants of their uniforms and PE kits. Is it wiser to visit the grimly organised "back to school" departments in shops now and use up holiday spending money, or risk waiting until the end of August when we'll probably be even more broke, and the shops won't have anything left in the right size? Decisions, decisions...

Meanwhile, a polite little email arrives from the holiday company. Could, ahem, I pay the outstanding balance, due a month ago? I hadn't factored that into my summer spending. Somehow I thought the cottage itself was paid for. Sigh.

So, instead of my usual pre-holiday round of new purchases – jelly shoes, snorkels, colouring books, sunhats, boogie boards (and that's before I've started shopping for the children) – I am playing Mrs Scrimp. So what if last year's fishing net is a bit battered? Nothing a bit of gaffer tape won't fix. And nobody actually got round to playing Rummikub last summer. But they will this time.

So, broke, disorganised and not at full strength health-wise. This can mean only two things: my husband will do the packing, and my parents will join us on holiday. Eek and double eek.

For a control freak like me (in all areas other than financial, yes), this is not an altogether comfortable prospect. I might arrive to find that I'll be swimming in my underwear (which is lucky because I'll have 30 pairs of pants packed). The children will wear the same clothes every day, and all of those will be slightly too small, as my other half's idea is to take only stuff you don't want to bring back.

This worked well in India, when everyone carried their own luggage on their back, and it was a delight that the bags got lighter with every passing day. In Wales, via car, with a distinctly "changeable" weather forecast, I want to have everything from wellies to bikini, all the right size and in good nick.

It may or may not be a good thing that I've discovered that my online clothes porn, the Toast catalogue, has an outlet shop in Wales, only an hour from my cottage. I will be able to buy, should things get desperate.

This is of enormous comfort to me. I can leave the cooking safely in my mother's hands; child-wrangling is down to the father and grandpa; mess-making and shrieking in the sea is in the children's hands, and I can do what I do best: shopping.

Not unrelated to this hotchpotch of spending and saving is the continued spectre of economising. The original plan was to buy a huge amount of food from the health food shop and farmers' market near home and take it with us (I don't like to be too far from food at any moment). But that would prove prohibitively expensive, and I don't think any child wants to travel for five hours with an organic chicken on their lap.

Instead, I've done some laptop research – on one of those bed trays with a hard top and a cushion underneath. Oh, the shame. Tesco deliver to the postcode we're staying in, so a giant amount of food will arrive just after we do. It feels like putting a deposit down on eating well. And that's just fine by me.