Some of the online shops are really slow – what annoys me most when they take your order but turns out the item isn't in stock but no-one tells you or e-mails and you log in 5 days later to see why it hasn't arrived to discover they don't even have it!
CRC and Wiggle never seem to manage next day these days but I think the degradation of the Royal Mail has something to do with it.
I order a lot form Parker International and they are the SLOWEST. I ordered some stuff last Tuesday and paid £3.95 for "priority despatch" for some stuff I really needed for the weekend then ordered a campag cassette which I didn't need in a rush so it was free post. The cassette arrived Friday and it said the priority despatch (via parcelforce 48)was due to arrive MONDAY! I was even more annoyed when it didn't come until Tuesday!
JE James are very good – their next day option (via APC – £5)always seems to come on time.