Peter, you bought a new plane and there a budget makes much more sense as you start, supposedly, from a squawk free, zero time platform. But a 30-50 year old plane with journeyman maintenance is very hard to budget.
I think the questions to be asked are: Can I afford to buy this plane? Can I set aside at least as much as I bought it for, for maintenance the first year? In that case, I think it's viable. So this gentleman should buy the aircraft for £13K, but make sure he has another £13K either saved up, or readily accessible over the next 6 months.