Old John:
Drempels:
beefy4605:
if your sure you want a coolbox and not a full on temperture controlled fridge then look at Halfords . They have a big 40 l one that is 12/ 24 volt as well as 240 so you can run it at home on the 240 volt , in your car on the way to the truck on 12 volt and it also runs on 24 volt in the truck . I had an older version (no 24 volt ) but it worked well from the 12v plug in the truck never had a problem with it in 2 years .
Link to the newer version -
https://www.halfords.com/camping-leisure/camping/coolboxes/halfords-40-litre-mains-and-12v-24v-electric-coolboxThat looks bang on, cheers mate! Waiting for someone to get back to me on Gumtree, but if they don’t I think I’ll be heading to Halfords later!
I bought a Halfords 24 litre powered cool box earlier this year , and have been very pleased with it. (40l model is rather big, 24l fits perfectly in Scania on the floor, between front of passenger seat and dash)
It is a little small I you don’t have a chance to replenish through the week but it’s not been a problem really. There is no temp control , but the spec is that it cools to 18deg below ambient. It’s a little noisy, but unplugging g at night is no bother as it is still well cold in the morning. It won’t pull the battery down if you do leave it on overnight but will if it’s on all weekend.
From memory it was £42.
Went to collect the Gumtree one and whilst I was out Mrs D bought me a Halfords one like yours! 
Using the Halfords one, so far so good!