I personally would leave the Red VR6 conversion alone, I still think the engine is too heavy for the MK2 shell, and also there are too many poor conversions done.
The Oak Green is very nice, but personally i'd go for the that D plate 16v, if it runs as good as the pictures look it'll be an amazing car. Also the early shells are known to be the better for stiffness.
As oackgreengolf stated, the mateymatey website is very good, I used it before buying mine. Even though it is getting hard to find a good one now, don't rush into it, look at as many as you can and take them all out for a drive.
The prices for those in the links are getting close to top money, so there should be very little bodywork issues and the interior should be almost mint.