It is not necessary. My employer offers the lot, but we have a lot of students with PPLs come in to do the CPL/IR.
The advantage of doing both inthe same place would be familiarity with the area - I never knew the Bournemouth area until starting my course, never flew here until the CPL. However if you think that is important you could do the last few hours of the 150 you need before starting the CPL at the new airfield.