Just to clarify, directly from the CAA
For the overall 200 hours of flight time that is required before undertaking the CPL(A) skill test you are able to use 100 hours of PIC time that you have accrued in helicopters. There is additionally a requirement to have 100 hours of PIC time in aeroplanes as part of this 200 hours before undertaking a skill test. This 100 hours must be in aeroplanes. You can therefore use 100 hours of helicopter time and the other 100 hours would need to be PIC in aeroplanes.