A 'proper' charger won't be 12V and mains, but if you must, a much better charger than all those suggested so far is the
Fusion RC LX61B Pro. At £99.99, cheaper than the Bantam, and it'll do 8A, not 5, 120W charge power (on 12V), and 90W charge power on 230, rather than 50W with the Bantam.
The Bantam was a good charger, but it is so dated now, I cannot see why people still recommend it like it's the best and most technologically advanced charger on the market.