I used tesco ones for both my boys - they gave me BFP first time.
Interestingly though, last year I had an ectopic pregnancy and although I was late for period- the CB test gave me a neg.
A friend bought round some the of cheapy tests from eBay - and I got a positive and a neg. I ordered some myself, 2 days later I did 4 of them and got BFP!! I took another CB test and it still gave me a neg!!
Pregnancy hormone doesn't rise as high when the pregnancy is ectopic so I was surprised that CB didn't give me a BFP when I first took it!
I now have a stash of the eBay ones in my bathroom just in case - I would trust them to tell me from the day I was due - I personally wouldn't test before then anyway 