I have just bought some MMX and Nobby Nics tyres, I have followed the advice and started mounting the tyre away from the valve and kept it in the central grove but the last 2-3" are impossibly tight to get on. I have tried tyre leavers but I didn't want to push it (so as not to damage the rim). Any advice?

Use plastic tyre levers e.g. the blue Park ones. They'll break before the rims do – some tyres are a right bitch to get on those rims. The benefit is that they will be easy to inflate.

GB

I have already broken 3 plastic tyre leavers!

Which brand were they? El cheapo or Park?

El cheapo!

i like the big yellow pedro levers

That'll be why. Get some decent Park ones – they are loads better than crappy ones. Plus, hold the wheel upright and, starting at the top, force your hands round the tyre towards the bit which is not on the rim – the idea is to try to gather up the tyre in one spot to make it easier to get on.

washing up liquid as lube?

Ok I have got the tyre on but I cant now make the tyre bead go next to the rim edge it just want to stay in the central grove, I have used a gas canister but it made no difference

compressor!

does anyone know if the car tyre compressors that you power from the cigarette lighter will work or is down to my local bike shop (or garage if I am feeling brave)

Those car compressors won't work, they dribble the air in until it eventually gets to pressure. You need a high rate of air to get the tyre to pop on and seat.