I have used the JR Inkjet kits click here the Jettec kits click here plus the InkTec kits click here My favourite one is the InkTec as this comes with an air balancing device.If you go to the InkTec site, you will find a nice video on ink refilling.
You should be able to get the JR from most places including Asda/PCW stores. The JR and InkTec are also available from Choice Stationary click here
If you want advice on refilling, try these sites click here click here click here
Word of advice, if it is your first attempt at refilling. Wear gloves and have plenty of paper as a work area. It can be very messy if you are not carefull. Personally, I have now gone from refilling to using compatibles.