Is there a difference between Clear Blue and Clear Blue Easy HPTs and if so, which one is most sensitive? I'm 8 days post BD (not been charting ovulation yet) and have used Boots Twin Pack Pregnancy Test which is still coming up as

(test done afternoon not morning) - does anyone know what sort of HCG levels it picks up? Granted, I would have had to have had a very late ovulation to be PG and wasn't really very hopeful at first but I'm several days late now for AF and have a few symptoms and want to make sure I'm using the most sensitive HPT. I'm in the UK and I think there's a difference between the Clear Blue HPTs in the UK and USA from what I can find on Google.
I have 2 ClearBlue HPTs which I've not used yet - I'm holding off for an early morning urine before my next POAS - if anyone can think of a more sensitive one you can get in a 24 hour Tescos, info would be much appreciated. I think they had a Clear Blue digital too - is it worth buying one of them instead of the ones with lines? Thanks.