Well speaking as a fellow CTR owner here is my advice...
Keep the CTR (shock). Wait until you settle in London and have a job etc before deciding what to do. I live and work in London, so my position is fairly similar. My car only gets used at weekends and occasional evenings, so its a toy rather than a method of transport most of the time. As a toy I would rather have the CTR than the ED30, don't get me wrong the Golf is much better all round car, but on a spirited drive I think the CTR would be more fun. If you will be using the Golf to commute then it would be different.
The CTR may cost more to insure (although i'm sure you can get that quote down, try Chris Knot), but the depreciation on the Ed30 would be more than the CTR, so running costs would be very similar.
But wait until you have a full idea of the costs of living in london for a few months before you get tied into a new car purchase. You would not want to get the Ed30 then realise that your costs of living were greater than expected.