You don't say what type of batteries they are… I expect, with the drill being 8 years old, they are probably nickel-cadmium or NiCad for short. These batteries are infamous for manufacturing a "memory"… that is, if you've never let the batteries discharge fully, they take a memory set which they reach in a very short time. There are sites that describe "deep discharge" of NiCad batteries to help overcome this problem… but it's all academic since, as you've discovered, the manufacturers of the devices in which they are installed have all migrated to the Lithium batteries which, apparently, don't have this problem,
So… long way of saying… you're gonna have to shell out the money and buy a new cordless. In fact this was discussed on a recent thread maybe under "How it Works"…
Here in the U.S, Rockwell makes a great drill/driver in various voltages. I have an 18 volt one and can get about 1 year out of the batteries. Nice thing is, Rockwell has a "Free Battery for Life" program. When a battery refuses to charge a quick e-mail to them is answered with a new battery in about 10 days… postage paid. You might see if they are available in the U.K.
Think of it as a belated Christmas present! Merry Christmas, by the way...