I'm thinking about getting a refill kit for my HP Deskjet 5550 (still waiting for confirmation from the JR inkjet people if my printer is compatable). Just wondered what other people's experiences have been. Are they worth a try?

Don't bother, more trouble than its worth. I had a nightmare with them and I've heard loads of stories where the ink has actually knackered the print heads. Stick with the compatibles.

Well the thing about the carts is they have print heads built into them. The heads are designed to last about as long as the ink. Once you start refilling you are overworking these print heads. And all this is aside from the ink mess. Like green_blade said, compatibles are the way to go.
Try http://www.supermediastore.com for carts. I have ordered from them before and they have about the best prices on the web (especially for Epson carts)

the heads work 6 or 7 times the amount of inkt that is in the cartidges
works great for me - i reload my cartidges 3 to 4 times, then throw 'em away. i get mine here: http://www.millennium.be/
way cheaper this way, colour cartidges costs waaay more, it's worth the hassle of reloading (just put a needle in the cartridge, done in 20 sec / color

Moving to Consumer's opinion forum

you dont say were you are in the UK go here www.xsct.co.uk

I've refilled mine 3 times so far and was told that I can probably refill 6-8 times. I use the HP 712C printer w/ the #45 cartridge. I too have recently purchased the HP 5550 printer and hoped to refill it once my ink runs out. The online store that I bought my ink from sells a kit for the 5550 and gives instructions on how to refill http://www.vamex.com/ the kit cost $20.00 and they have one for colored cartridges as well. I hope it works. Good luck