As people have mentioned.
Ghostbikes
Racevisors
Helmet City
These are the main stores I would buy from, Helmet wise, I try it on in store check for online prices to compare, ended up getting my helmet for £30 less than in store & there throwing in 2 Visors + 2 Pinlocks with tear posts. Can't go wrong with that. spoke to a guy on the phone at helmet city he couldn't ask for a better chap to deal with. I find it nice when you get someone on the other end who knows & is interested in what your asking rather than just going off a script.
I bought a double bubble screen a couple years back from Ghostbikes, ordered 4pm came next day 8am. Cant ask for better service.
Just so people are aware, when a item is being delivered you can sign for the item as damaged even though it's not. Everything I sign for I make sure I put down either, Unchecked or Damaged. So if there is any thing to report, I can back myself up, if not then Royal Mail don't care they just leave it. It's your responsibility to take it up with the supplier, so they then take it up with the courier.