Hi Zeeky
My sis and some friends have M&S sofas that are good but since I have been looking to buy a sofa the last few years the new ones really seem to have gone downhill - comfort wise at any rate - they seem like they are using cheaper springs and fillings :( ditto most of the ones in places like john Lewis and laura Ashley etc
There were some comfy sofas in Multiyork - I found this one comfy but I liked the look of this one
But the one I liked the look of wasn't quite high enough for me to rest my head on or deep enough whereas the other one was - but I didn't want curly arms that took up lots of space. And whilst they say that sofas can be tweaked to change both these things it was never on the designs I wanted!
If you do want their stuff, don't buy if the sale isn't on - there is frequently a sale on - usually for about 30-40% and occasionally for 50% - think they just have enough 'off sale' time to comply with the law IYSWIM so think of their sale prices as their real prices and the other prices as a bonus for them...
www.kraftupholstery.co.uk - is the place I mentioned previously. They were really friendly and knew their stuff. I think they basically do a price 'per half seat' of a sofa - and I think a full seat is 20 inches. So if you wanted a 3 seat sofa that would be between 51 and 60 inches wide, a 3.5 seat sofa would be anything between 61 and 70 inches wide, a 4 seater would be anything between 71 and 80 inches wide etc. And then you just pay a per metre charge for the fabric they use to cover it.
plus you get to choose the style of all the different aspects of the sofa - back height, seat depth, pitch of the back, arm style, fabric obviously, piping or not, different positions the seams can be (around the arms - I'd never really thought about it before) - you name it, you can say up a bit, down a bit, seam here not there etc. If you ask for something that wouldn't work they would tell you though obviously! and have lots of stuff in the showroom that you can try out to get different ideas. Then have the arms from this sofa, the filling from that one, the seat depth from here, etc etc. They also have loads of fabrics to choose from - collection books from loads of places both well known and others that are more 'trade' - they were also happy to point out the ones that were significantly cheaper 'trade' fabrics but made by the same people as some of the big names where you pay in part for the name. And particularly if you are going for a plainer fabric (rather than an obvious Romo or Sanderson etc pattern for example) then you can cut the cost of the fabric in half or more for the same quality.
I'll stop there. I can bore for England on sofas - or rather the lack of comfy ones available in the shops these days but shout if you think of anything else - I've been to most places selling sofas around MK, Northampton, Buckingham, Bicester, Brackley as well as plenty of the london places. DH reckons I have wasted far too much of my life looking for sofas - if it was up to him he would have just popped into argos and done eeny meeny miny moe 
and then complained for years about how badly they have worn and how uncomfortable they are!
As you can tell I haven't let him do this so we are still sitting on our old sofas But one day I will get the sofas I want (slightly complicated by the fact I also need to choose curtains and no point getting sofa until I get curtains as it might be the wrong colour, easier to get a plain sofa in any colour to match the curtains... But at least I know now where I am aiming to get my sofas from!