Every 20 minutes, takes a couple of hours. Can be expensive but if you book in advance and/or travel off peak not too bad.

www.virgintrains.co.uk

You would then need to get to LHR itself, from central London you can use a taxi (very expensive), Tube+Heathrow Express (expensive) or the Tube (slow but cheap).

It appears, according to a Google map, to be right next to Terminal 4.

You also have the option of flying - BA flies from Manchester to LHR.

Neil