I use Donald Russell regularly for beef/steaks. It's not cheap but very good, especially the chateaubriand. I was not so keen on their poultry. Just last week I tried Broadstripe for the first time, it came recommended and is much cheaper than DR. So far we've only eaten the quails and I've never cooked them before so I can't really comment, plus some pork fillet which was good and very lean and a mere £3. I also have bacon, sausages and chicken in the freezer & I think tasting these will be a much better 'test', e.g will the chicken be tender, will that yukky white stuff ooze frame the bacon, will the sausages taste of meat?!
www.blackface.co.uk/ are absolutely fabulous. The meat is very good quality, from wild/extensively reared animals and reasonably priced. Delivery is good, the stuff is well packaged and insulated. We've never had a less than good experience with them.
I'm not sure whether they deliver UK wide but Macbeths is absolutely fantastic. I do an order every few months and freeze loads and the quality of the meat is really beyond compare, much better than our local supposedly brilliant butcher.
We use Laverstoke. It's certainly not cheap - but excellent value iyswim. The meat doesn't shrink, tastes fantastic and there's absolutely no wastage. They are also lovely to deal with. (It's also resulted in the first time that someone has complemented me on the mince in a lasagna )
I can't recommend their smoked back bacon enough. We buy it as they don't use nitrates in it and it's so well-flavoured you only need a rasher or so, whereas before I'd have used a whole pack.
I used to buy meat from Riverford but it's not a patch on Laverstoke. Riverford's sausages were too heavily seasoned for our liking as well.
(And apologies if this is off topic but if anyone can recommend a good online fishmonger? or am I, like M&S, asking too much?)