Thank you to everyone for your help and advice. Its what makes this community such an amazing group of people to be part of.
This is what I've decided to go for.
These have been used on artic expeditions and such like. The guy Tim, who supplies them has a good customer service reputation and is really helpful. He uses one of these to power his air pump for his own rib and a paddleboard. It has a CLA socket and adaptors for other 5v gadgets.
And the booster has received very favourable reviews in tests on jump starting cars. Although primarily for my rib, it will also help in my car which has a diesel engine and needs a bit of ooomph to turn it over.
The Overland plus is not the cheapest. But hopefully, it will be reliable. I am buying 3, 2 of which are for my daughters. I dont normally spend that much on Xmas presents. But I worry about them being stuck somewhere waiting for a breakdown truck. Flat batteries are more commonplace since covid meant working at home for many. Its also a bonus that it will charge phones and other similar devices. So it will also help if my radio or mobile runs out of charge when I'm out for the day.
I will post my experiences once I've had it for a while and had a chance to try it out.
In the meantime , thank you once again everyone.
And best wishes.