I do them too and have about 5 firms on the go, the results are variable and some pay you in vouchers (argos etc) so still good as you can use them for pressie shopping. I try to avoid most of the ones overseas though one (Pinecone) is ok and you get �4 luncheon vouchers for each survey even if only 3 questions long.
Another option is to be a mystery shopper very good if you can drive, a family member does this and gets free meals etc or payment if its doing something like a report on customer service.
Good luck
M