My point is the following statement isn't strictly true:
if you want some cheap fun then making something slow faster is the way forward, tuning a vr6 is very expensive.
Yes you can buy your 8v for £500, but you'll have to spend a few hundred to get to 16v level, which as stated you can get for around £700.
The same applies to the 16v and tuning that, you still have to spend a fair bit to get to vr level, which you can easily pick up for a grand.