Just been in my local Tesco Metro in Macclesfield and noticed these rechargeable 9V Energiser batteries for 75p. the tag on the shelf isn't one of the usual sale type yellow tags - see picture below.
Online these are still £6.70 and looking round the web that is about the same price everywhere.
Please note this is instore and not online.
Some blurn from the website follows:
An Energizer rechargeable 9V (PP3) battery. This battery can be recharged up to 1,000 times and is ideal for frequent and heavy use.
Energizer Rechargeable NiMH round cell batteries are available in all sizes, including AA, AAA, C, D and 9 Volt sizes. They can be recharged to full power at any time using a broad range of chargers - including the family charger, compact charger and ultra fast charger. Since the cells are rechargeable up to 1000 times, they're a good economic and environmental choice. It makes them ideal in high drain devices such as portable CD players, remote controlled toys, hand-held games, palmtop computers or any time you want to replace your standard batteries in your household's battery operated devices when you use them a lot.
Hope the pic link works below: