I'm buying a new house at the moment having lived in a large shared house for a while and will be doing it up, but I was just wondering, if you were starting from scratch how many cupboards etc would you want in a kitchen of a 2 up 2 down terrace house? They promote them in units of 8 when I went to B&Q, but that didn't seem like that many (although that didn't include the sinkand cupboard underneath that).

Like bikes: n + 1 where n is the number you already have.

Those mock up's are for comparison purposes only. You don't get much, you're right. Also one of them is for an integrated extractor!
Best thing to do is fit the kitchen to the available space and don't skimp. You will always fill the space somehow.
Those type of rooms are usually done in an L shape. Sink, washing machine etc under the window. along the internal wall, corner base unit, An L shaped one usually won't fit, oven and hob, drawer pack, couple of 500 or 600's. Chimney style extractor over hob, ducted behind the pelmet. Corner wall and as many other units as you can get in.
The room sizes vary greatly though, from around 4×4 meters to just under 3×3