best sites are the distributor websites e.g gridrecordings, load media, co-lab recordings, ganja recordings because they get the first cuts of the promos and new releases but they usually get sold out within a couple of days.
I use HTFR, Redeye, Juno & Nu Urban. HTFR is best for me cus in my area we have a dodgy postman or sumat cus ive had alot of records not arive. Out of the above HTFR was the only1 to resend them straight away with no questions asked and no extra charge! Also check out some of the e-bay record shops for cheap and rare vinyl but be carefull only go on the 100% sellers !!!