thisfrom an earlier thread I thought there was also an M&S factory shop, if you are in the right region.
If you're in the Midlands, Westbridge Furniture.
They manufacture furniture for M&S, Next, John Lewis etc. and have an outlet at Blythe Bridge (Stoke-on-Trent). Massive discounts versus buying from the retailer, decent quality and good service. Can't recommend them enough.
http://www.westbridgefurniturestoke.co.uk