But I was thinking it would be nice to have something to warm my body so I had a look at motorcycle garments, there are quite a few available but all over £100 and then you have to find something that fits you, etc, and you have to plug it in!
Anyhow I came across this https://www.ebay.co.uk/itm/For-Motorcycle-ATV-Bike-Warmer-Winter-Carbon-Fiber-Seat-Heater-Kit-Heated-Pad/223143529789?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 which looked interesting,
for around £11 you get the pad and the wireing loom

I put mine lengthways on the back of the seat back, plugged it into my 24 - 12v inverter and took the dog out, It's really good you can feel it through 3 layers of clothing. I measured what it draws from my 26v pack with my clamp meter, .4a on half power and .8a on full.
No wireing to do exceot from connecting it up to 12v, you choose off/half/full power using a 3 way switch provided. The loom has a relay in it too.
Much easier than a heated garment, there's nothing special you have to wear, it's part of the chair.