Yes, the one I found was 915.5110 and it must be for Western Europe.

The following is a list of maps compatible with my firmware. Does anyone know if any are UK only?

845.2644
880.3811
905.4800
910.4963
915.5076
915.5106
915.5108
915.5109
915.5110 (this is the one I tried and was 2.3GB!)

Thanks!