Halfords have some Camelbak products on offer and in their 3 for 2 offer as well.
E.g. Brush Cleaning Kit down to £5.00 from £9.99
Hydrobak 1.5l pack down to £15 from £24.99
1.5l Omega reservoir down to £10 from £18.99 and 2l down to £15 from £24.99
All Camelbak are 3 for 2 as well so you can get the replacement bits like the big bite valve in the deal.
If you and a couple of mates want the M.U.L.E. it works out at £43.33 each! Find a price even close elsewhere...
Can't link directly to the page so just search for camelbak in the search box.