Thanks for the input guys.
Doing the IR first would indeed save some money - as things stand at the moment once I have completed my 100 hours P1 I will still have another 10 hours to do (either dual or PIC) and so the IR will obviously eat up that flight time. It will also mean I am less pressured over the summer as I will only have the CPL to do in my tight three month window, as opposed to the CPL and then the IR.
What I am concerned about is the skill level required for the IR. I've often heard the IR is much more difficult than the CPL and that the CPL course and hour building prerequisite will help you prepare for the IR. Therefore, doing the CPL followed by the IR seems to be a more natural progression.
I'm just wondering if this is indeed a fair assessment or if I'm exaggerating. Many modular providers also seem to suggest the CPL is taught first, with the only exceptions being in case of weather (i.e if starting the CPL/IR in winter, IR comes first to minimise weather disruption and delay CPL until milder weather).
It's very difficult to tell from my naive position where I am relative to where I need to be for the CPL/IR in terms of skill level. The only indications I have are the skills test tolerances for the CPL in terms of maintaining heading/altitude/airspeed and I don't think I am quite there yet in terms of the altitude tolerance (I do still bust +/- 100 feet on most flights). I am sure there's more to it than being able to fly accurately too.