Sir T,
try a search in this forumon Epson clogging. I expect you will find a lot of info on the subject.
http://forums.dpreview.com/forums/forum.asp?forum=1003
From what I have read in there Epsons are quite prone to clogging if they are not used with some frequency.
Cleaning them uses a fair bit of ink and if that does not work a head replacement is the option.
For what it is worth, HP ink cartridges are probably the most costly but the print head is incorporated in the cartridge, ergo, when you replace the cartridge you are also getting new print nozzles. When I was looking for a printer to do photo quality printing I came to the conclusion that the Epson using Ultrachrome inks (archival pigment inks vs Dye type ink) sounded like the best for overall quality and longevity but I ended up with an HP for just the problem you are having. The HP eats ink but the results are really very good, especialy using their best photopaper and the Photo Black cartridge. That is the one with three levels of Black (or gray I guess).
If I was printing more often I would still like to go for the Epson R800 or equivalent as by all accounts it is just that little bit more faithful to the colours.