Thanks, heaps, everyone! I've found this very helpful and have assembled a little list on what specific products to look for/avoid when I go shopping. If anyone has anything to add, I can edit this post to reflect that, in case this is useful to anyone else.
Recommended:
"The only [Quorn product] I use regularly is the Quorn Pieces (fake chicken) which are useful for soups, stews & stir fries."
"Also check out Cauldron brand - available in most big supermarkets, they do various kinds of tofu as well and burgers, pates, sausages and more."
"I found most of Tesco's veggie burgers acceptable. The nut cutlets were probably my favorites."
"I did like [Quorn's] cottage pie if I needed something quick."
"...Cauldron Brand from Sainsbury's, 3 for the price of 4 right now - buy loads and freeze). As Andee mentioned, it's great in stirfrys, also great in currys, soups, or just marinated and grilled."
"And my favorite meaty substitute is dried soya mince. We use Sainsbury's own brand, and it's unbelievable cheap, very high in protein, and has nothing funny added. It can go into anything that calls for beef mince. My favorites are chili, tacos, spag bol, lasagna, etc."
"Here you can get [butter substitute] Pure (in the green tub) which is soya "butter" in most supermarkets and it's really good stuff."
"Also, the spinach and feta Quorn sausages are TO DIE FOR!"
"And try Cauldron's veggie pates - the tomato and basil one is the best of the range, imho."
"now, i really dig the quorn stuff, but i have to limit it to the fake chicken and fake bacon stuff."
"I use the [Quorn] chicken pieces a lot, for stir fries and pies. Their chicken burgers are pretty good too."
"We get through loads of Realeat mince. It used to be sold in Tesco but is being phased out for their own brand, which isn't as good."
"Cauldron sausages are the best, but tesco and Sainsbury now do very good ones too."
"As well as the above, we get sainsbury burgers and hotdogs sometimes. They are actually made by a firm called Tival, who also make shnitzels, nuggets and a few other meat free products. Tival stuff is also sold in health food shops, and in supermarkets is likely to be in the kosher section if you have one."
"I absolutely love the vegetarian Sainsburys hotdogs."
Not recommended/avoid:
"Stay away from most Quorn products, they taste a bit funny to me."
"I agree with Britwife that most of the Quorn products taste a bit funny."
"We used to use Quorn alot, but I've been reading about some disturbing reactions some people experience from Quorn products."
"I think [Quorn] sausages are bland and the burgers are like cardboard."
"Quorn stuff contains egg." (So, it's not vegan.)
"the burgers i can't do--any veg burgers--it's a texture thing. same with sausages."
"the linda mccartney stuff is way too salty."