Thank you everyone. I shall look for a Ctec trickle charger. I’m assuming this then needs connecting to my car all the time: am I right?
No. It doesn't NEED connecting permanently but CAN be.
I personally don't like to have a charger (cos even the intelligent/ maintenance ones are just chargers) connected to the car all the time....just in case!
I use mine to top-up the charge about once a week. Once all the lights come on to say it is fully charged I disconnect it. Some leave them connected all the time. Personal preference.
If your battery doesn't have a breather pipe connected (or even if it does), it is a good idea to leave the boot open when a charger is connected, if you can. Batteries produce hydrogen (albeit in tiny amounts) when charging, which is extremely explosive. Highly unlikely it could be a problem, just a sensible precaution IMO.