Nick,
As to whether you wish to complete a single or multi CPL, it's down to a number of things, cash included.
I believe (although I could be corrected) that you need a valid MEP rating before starting a multi IR. This being accurate, the choice is between a singe CPL (25 hrs) followed by an MEP (8 hours), or combining the 2 as a Multi CPL (28 hours).
In simple terms this saves 5 hours of single engine time, but if only it were that simple.
I did a multi engine CPL and found that you need to be spot on with single work before transitioning to multi work, because if you can't navigate or fly with accuracy or on basic instruments, by that stage, the learning will be very expensive. Fixing errors flying a multi costs an eye watering amount of money.
I managed my CPL with 21 hours on the single and exactly 8 hours multi getting a first series pass. My failure on my first attempt was asymetric work unsurprisingly. I am however aware of colleagues who needed 50ish hours to complete their multi CPL.
The problem is nobody tries one course and then the other. It may simply come down to whether or not you prefer PFL's in a single or asymetric circuits, go-arounds and engine shut downs in a multi, because that is fundamentally the only difference between the two.
Regards,
Obs cop