Unfortunately the other meat-free ranges are usually not free as they are soya-based instead of quorn which is a brand name.
That said the Asda Chicken Style Fillets (twin pack), frozen are free. I've haven't tried these so can't say if they're any good or what they cost.
The Asda meat-free mince is 1.5 syns per 100g raw weight. Not too bad and the 454g packet costs £2.00 which is a bit cheaper than quorn. A lot of people, me included, think it tastes better than the quorn mince.
Their meat-free meatballs are gorgeous and are only 4 sins for the 400g bag. There are about 28 meatballs in the pack so it works out at only 1 syn a portion if you split it between four meals. These are also £2.00 for a bag.
Hope this helps.