Arp,
The atlas by Alan Stubbs gives the flight period for
C. pectinicornis as May to July. The atlas is published by the Biological Records Centre and can be purchased from them, see:
Biological Records Centre - Publications
The draft keys may be available from the UK cranefly recording scheme, you'd need to contact them direct, see:
The Society for the study of flies (Diptera) / Cranefly Recording Scheme
Alan Stubbs is working towards a cranefly book, to accompany his existing volumes on hoverflies and soldierflies.
Cheers,
Martin