Granarybeck, I´d recommend the Ibishotel at Coquelles (right next to the Cite d´Europe (the big shopping centre at the exit of the tunnel French side). CLean rooms at a reasonable price. www.ibishotels.com if you want a look. Also 2-3 other cheap hotels right next to it, can´t remember the name of unfortunately. Often no need to book!
J9 (15 mins away) of the M20 has a travel lodge and there's also a similar one by J10 (just on the A2070) - both Ashford. Don't know of any recommended b and bs but there are certainly loads around. Folkestone would not be any quicker than Ashford by the way as the turn off is before the town right off the M20 - Cheriton is the nearest place.
I've stayed twice at a B&B called 'One Step Beyond' (the last one on the list above). It's a lovely family home, situated in a small village (Etchinghill) just 1-mile from the Eurotunnel terminal, with very homely B&B accommodation, a decent sized room, spotlessly clean, en-suite shower, TV and tea/coffee etc. It cost me £25-£30 and I enjoyed a very hearty breakfast!
A great find, but not very well advertised, hence the link to the local village pub above. There are half a dozen other B&B's listed there too, but I haven't stayed in them.