GYo - From what others have said, I'd say First Response is a good reliable one. I only have moderately cheap ones - there are cheaper out there....
I have the ACON Early Detection tests which are supposed to pick up from 10hcmg (or whatever the unit of measure is!) which is the lowest levels that you can get tests for. I use the access diagnostics website and I have a discount code (and I'm a member ). The discount code is available for all in the TTC group and was value5% but I think it may have changed...unfortunately I can't access my home emails from work so can't check the new code - I'll try and remember to post it later. They also sell FR so probably worth comparing prices with supermarkets.
Re symptom spotting - I don't think its ever reliable to start as majority of symptoms are same for AF as early pregnancy...but it is good fun - hence me taking the piss out of myself by 'symptom spotting' at CD21.
Actually, I write down how I feel and any 'symptoms' each month, which has enabled me to rule out pregnancy as each month I now know I get sore boobs, weepy, tired and crampy about a week before AF. I also know that I can have none of these symptoms and still not be pregnant!