MX 3litres cruiser, cooking-grade AF , still going for £29.95 in N Essex chandlers. Been the same for several seasons, and good enough for my purposes. Have yet to see this mail order, or even cheaper delivered.
Trago Mills in Newton Abbot are doing 3L of Cruiser UNO for £50 at the moment with vouchers back depending how much you spend. We have found them cheapest in the SW for all International products.
If you drive along to Yachtmail on Lymington quay they have always been much cheaper than F4, but I dont know if they do Micron Extra. Since the shop has been refurbished, they have been more a boutique than a chandlers. /forums/images/graemlins/mad.gif
Also have you tried Nick Cox, along at the LYH entrance - just been completely rebuilt with a lot more space, and very helpful people too.
Aladins sometimes have 5 litre can's as well, there quite big and awkward to decant especially when it's windy. I got luke to order me a can before xmas. The can has £130 on the top but I think I may of left a deposit of £10 on it with some other stuff that he ordered for me. There is always room to negotiate with Luke. especially if you buy other stuff.....
He got it quickly so i suspect he got it from vitesee marine down the road. If i could of bothered i would of got it there myself but i like giving luke my business !
We used the Seaguardian and it was really VERY effective, been on for two years now, about 7-8000 miles sailed and only minimal growth of slime. Scrubbed under water a few times while away and held up well. Bought it from Shepards.