James, a 2 stroke 250 is an ideal bike to learn and develop your riding skills on. In my opinion far better than starting on a larger bike.

As you have never owned / rode a 2 stroke 250, you will find the RGV to be a good bike and fun to ride. But once you have rode both, IMO the NSR is far superior with regards to engine - torque & power when delimited (except for the MC28 which is more heavily restricted), build quality, Engineering etc on all NSR models. Plus they look far better. I used to have a RGV250N and now have a MC21. No way would I ever go back to an RGV.

MC18 parts are getting harder to find, but that should not stop you buying a MC18 completely, just something to consider. If you could get an MC21, you will find parts supply is OK. Honda still sell a lot of new OE parts for the 21, most certainly the engine parts and gaskets and many other items. You can also find just about every part for an MC21 2nd hand on Yahoo Auctions in Japan.

Rothmans colours do look nice, but if I was you, I would focus on the mechanical condition of the bike + intact bodywork rather than the colour scheme. You can always get a paint job later on.
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30