Hi mate. If you do an IMC rating early in your hour building, (i.e after 75-80hrs total time) it'll give you loads more options and confidence during the rest of your hour building, plus being a useful taster for the IR (so I've heard).
Im doing my IMC then Night at the moment, before I start any serious hour building at all. I also intend to do my multi as an add on to my PPL as soon as I can (70hr PIC required), and squeeze some expensive Seneca trips into my hour building.
One of my mates has done this and has got just 140hrs total (80PIC) and he's got PPL/Night/IMC/Multi, mind you he's a rich, clever sod who flies all the time.
I think you can do an IMC rating test on a multi engine aeroplane if you really want to be a clever clogs, but I'm not sure about that I might be wrong, and for a low time pilot it just sounds like inviting an accident to me.
My friend has just started the first stage of the ATPL's distance learning as well he says he's finding them a lot easier and more interesting because of his multi/imc, as he can "apply a practical basis to all the theory on heavier aeroplanes and IFR procedures."
Be careful though, because maintaining an SEP and MEP rating currency at the same time can be quite a handful apparently (unless your rich). All the best whatever you decide. Leeds for 3yrs. You a SPEME grad?