I've been asking my dealer several times about the spare, what price it is etc... He pretends I'm the first Civic customer asking for this spare wheel, he didn't even know Honda delivers a spare wheel at all! After my third call, the only thing he was able to tell me was that this would cost about 500 € (390 GBP), only for the wheel. He didn't even talk about a complete spare wheel set with bag etc. I insisted he took a further look in his catalogue but he said there wasn't anything better than this. Then he asked me if I couldn't find out what the exact spare's part number is, can you believe this!!??
Ok, i contacted a decent Honda dealer (a bit further away from where I live). On the first call, he told me immediately that he has always one spare set in stock and it costs 185 € (145 GBP). I had just to give him a call before picking it up.
Conclusion: never trust your dealer + I'm changing dealer!