Hi Rod,
That's a nice looking car you've bought, congratulations!
In answer to your query regarding batteries, I bought a 'Lincoln' 6-volt unit with the hard rubber casing from Lincoln Batteries in Leigh-on-Sea a few months ago. This is the same firm as 'Jollychuffy mentions in his post. Their service was excellent, the battery arriving the next day, securly packaged, and with concise instructions on how to set it up, as well as extra acid. They were also cheaper than anyone else I tried!
Hope this helps,
Gavin.