In reply to jungle:
In a break with UKC tradition, I'll answer the question you asked first: no, never tried it.
The longer answer as to what to do depends on you, your finances and the exact spot in the tent which has the hole. If it's an area that is an obvious high stress point, close to the pole sleeves, a guy rope attachment or a peg loop, then I suspect that no matter how professionally the repair is done, it'll pull loose sooner rather than later; I'd have second thoughts about using the tent in anything but gentle weather conditions. If the area is away from an obvious high stress point, in the middle of a panel of fabric say, then you might fare better, although it has to be recognised that a correctly-pitched tent requires all the fabric on the flysheet to be under a degree of tension in order to be taut. It's your call as to how much you'd trust its longevity.
Were it me, if finances dictated that I had to get it repaired then I'd pay the £40 to get it done by someone else; but I'd have a look at the cost of new, similar or better tents too and decide whether I wanted to put that £40 to a new tent, whether I needed that new tent between now and the new year and if I could wait that long, see what was in the new year sales. Or try eBay, you might strike lucky now that most people have stopped thinking about pitching a tent until the spring.
I can share your pain, having had to repair a tent with duck tape in the past whilst many miles from home. It worked, but I really don't recommend it unless there's no other choice.
T.