Not tried them myself but have heard several people say these were good - http://www.abelandcole.co.uk/
We used them for a while, but found we weren't getting through all the box, even the smaller one; so stopped using them.
Good quality veg and fruit though.
I've decided I'm going to get a veg box every two weeks this year instead of getting my veg from the supermarket. I'm going to use Riverford - looks good and I've heard lots of good feedback about them.
http://www.sunriseorganics.co.uk/weeklybox.htm
Also found this one which looks good. They don't let you modify your box, like Abel and Cole do, but all their produce is locally grown and sourced, which does appeal to me. Only good for Essex though I think.
Hi Celtia - don't know if this is of any use to you?
http://www.hotukdeals.com/item/580405/50-of-free-shopping-at-abel-cole-on
Suma wholefoods are a good place to order natural orgainc foods. We are part of a food cooperative that makes up their minimum order value of £250. They are good for basic staple foods and organic stuff, but don't do fresh veg. Plus they are a cooperative which makes them a nice, ethical company to deal with. Their website is www.suma.coop
If you think the minimum order is too much, i think you can also order direct over the internet at www.sumamarket.coop
Thanks,
Amy