Great, lots of advice there, thank you.
To clarify, I drink espresso the majority of the time, mostly from my Krups espresso maker (not the best, but has always made good consistent coffee to me) but also on occasion from my stovetop maker. On occasion, and to justify the purchse to my wife I will use a cafetiere, so an easily adjustable grind size is important.
Last night I won a new Gaggia MM on ebay, the price was very favourable to the mid £70's they seem to generally fetch. I looked at the MDF but they're not widely available (from a basic web search) and seem to be £150 ish delivered, so more than three times what I paid for the MM.
So that's that, for now. I couldn't really justify spending such an amount on just the grinder, once I've learnt the ropes on the MM as it were I can think of upgrading in the future.