Motorcaravan

If I buy one on the internet is it with acid ina My current battery, which is only 55Ah is in a very limited space so I'll need a fairly accurate size. My current battery has a tube running through the van floor landfill gas, they all have onea

Your best bet is a cyclic battery sealed lead acid gel,
there is no need for a vent or vent of the battery is sealed, it can be used any way, including up upside down.
If you're in the UK try here:

www.eurobatteries.com

(I have no connection) Excuse the pun!

Land for sale here too!