It's a truly tough decision to choose between a GTV or a Spider. The GTV has a superbly rigid, well-put-together feel and is bound to be a little more comfortable in the winter months, if only because of the rear side windows, glass rear screen, and extra headroom.
However the Spider has a little more glamour and will probably always have slightly better resale values.
There have been some amazing GTVs offered for sale on this forum at your £1500 price point or less. Be patient, another will turn up, and you'll know it will likely have been looked after and cherished.
The odd small fault is to be expected (often, a sale occurs because the owner has given up on something) and if you can fix it yourself, it gives an opportunity to bond with the car and be proud of your handiwork. If you absolutely want to avoid working on the car yourself, then either live near a specialist or face the fact that a GTV may not be a sensible choice.
consider the newer GT (156-based) instead.
I paid the equivalent of £5800 for my yellow Spider last year; think you'll agree that there are plenty of bargains to be had on the English market - the Australians pay even more than us Kiwis! Still, it's nice to have a 'sorted' example that I can just get in and drive. My hood cover paint is a little faded but that's about it.
I don't think you can go far wrong with either a GTV or a Spider, as each have their good points. I'm thinking of supplementing my TS Spider with a V6 GTV, to get the best of both worlds.