i use http://www.xscomputersupplies.com/ for epson ink. have used them for years now.

i always use copy carts!!

c70 black carts are £2.37 each and 1p for delivery

or go for the multipack:-

Epson Stylus C70, C70+, C80 Multipack Compatible Cartridges, 1 Black 321, 1 Cyan 322, 1 Magenta 323, 1 Yellow 324

Price: £9.46 (Including: VAT at 17.5%) + 1p del