Wow, a Startrite for £200, snatch their hand off (although the I still think it's a Wadkin AGS).
If it is a Startrite there easy to work on, spares are still available and they are highly sought after machines. There is no comparison between either a Startrite or indeed a Wadkin and a modern machine. One will last a lifetime the other will IMO be disappointing.
You are highly unlikely to loose any money, even if you but it and don't fancy refurbishing it, placing it on an auction site is almost guaranteed to give you a return for your investment.