12-13k should buy you a good Phase 2 Spider.
Phase 2 Spiders have spoked 16" wheels with 205 tyres,painted sills,chrome grille and a much more attractive dash and better trim,than a phase 1.
They also have 155 bhp if you get a pre 2001 car(Euro 3 emissions compliance knocked it back to 150bhp as per the 156.)If you can ,go for a Lusso to get the power hood,leather and air con.You will probably find that most are this spec,anyway.
Coming from a 147 the Spider will seem noticeably less refined although,you do feel more in touch with it,which is after all the whole point of a sports car.
Main things to check are rear suspension wishbone bushes and the hood for leaks.
Running costs are similar to a 2 litre 147.
Spend as much as you can afford and get the best, most pampered car you can.
With the imminent arrival of a baby we were considering selling ours,but as we have the use of a sensible company car aswell,we decided to hang on to ours for sunny days and Sunday morning blasts.
Thats the problem with Spiders,once you get bitten ,its hard to shake them off!
Good luck with your hunt.
PS Have a look at www.gtvv6.com
buying guide.A lot still applies to Spiders.