I've done a couple of similar projects - weight weenie on a shoestring. The last few grams always end up costing the most! M751 cranks are a good choice and the matching ES71 BB is also lightweight. M752 are a tad lighter and have a nicer shape IMHO than the 751. Weight-wise you can get similar results from an M570 with a UN7x BB.
A couple of other recommendations for £/g savings. Grips-wise, these £4/25g foam ones from ebay:
http://www.ebay.co.uk/itm/25g-Ultra-Lig ... 1087520199. If you have a standard-ish size seatpost size, these are £17 and ultralight:
http://www.cyclomonster.com/cart/gub-li ... -post.html.
For wheels, I'd avoid Shimano hubs for weight-saving, and if Mavic-rimmed go for 517s if possible. I've got hold of a couple of sets of 1st Gen Mavic Crossmaxes SUP (one set 1546g, the other 1596g), but in decent condition they fetch a lot. Also the 1st Gen Mavic Crossrides are pretty light. I found that cheaper second-hand options are Rolf - 'Propels' about 1600g and 'Dolomites' about 1750g ('Satellites' are heavier though).
Tyres? The reason I ended up at this thread - Exeter Man pointed out you might be interested in my Maxxis 330s currently for sale:
viewtopic.php?f=39&t=247660. [Though they are now sold, and I also realised I'd already sold you some Schwalbe Furious Freds a few weeks ago!]