5 string P bass neck pockets and stuff

I have a Washburn XB105, and for such a cheapo instrument it's very well finished and put together.

However, I would like something that looks a bit more - er - classy.

So I was wondering about sticking the neck and other hardware on a different body. Ideally I want a Presicision style, coz I like them and the Washburn has a P pickup. However, I need to know

a) how interchangeable are necks between brands? Do they have vastly different pocket dimensions? Could the scale length make some unusable (without moving the bridge I guess)?

b) does anyone do a P shape 5er body at an affordable price? c. £50/$100

c) does anyone do a P5 that costs significantly less than the £1k/$2k options that only seem to exist? I know Squier does one, but that has the J pickup configuration.