JB, just a thought but if a hot water bottle is inconvenient why dont you try a heat pad - they don't use too much electricity
and are like mini electric blankets about 16" square. and quite cheap to buy - and like the blanket they have 3 or 4 heat settings.
Geoff
Geoff thanks I think you are right, I need something more convenient now, I can plug it in under my desk...spaghetti junction under there...its a good job I don't have everything switched on at once!
I've done as search too, Amazon was at the top...hot water bottles and heat pads for back pain..ha ha...my new bottle is there with some customer reviews, had to laugh at this one...
This review is from: Cassandra Hot Water Bottle Double Ribbed (2 Side) - Colours May Vary (Personal Care)
I was disappointed when I received this hot water bottle to discover how small it is. My old hot water bottle, purchased in Boots in 2004 measured 9" (inches) by 12" (14.5" including the neck). This Cassandra bottle measures only 8" by 10.5" (13" including the neck), and thus holds proportionately less water, about 70% of the volume of my old bottle. With this reduced thermal capacity, the Cassandra bottle does not retain a sufficiently high temperature throughout the night to meet its purpose. I cannot decide whether it is the global warming faction or the health and safety brigade who have put pressure on the water bottle manufacturers, but it has deprived us of much needed warm comfort during long cold nights.
Made me smile anyway

I think I'll pay a visit to the local chemist where my son found the 'Cassandra'...mine is pink too! a fiver it cost, I'll bet they have heat pads and for less than Amazon and the like, any problems and it can go back...
Just need to get myself in the car! ...getting out is even harder but the thought of bringing home a heat pad this morning will help
I think all this is relevent to john mk2's question...heat pad or as a stopgap a hot water bottle for the LSS

JB.