Up late too then?

I would say the RS will almost certainly stock the connector but you'll have to polish your search-fu as without a manufacturer or model number it'll be difficult, although I think I got close (item number 512-8591).

That said, a quick google for 'battery pack molex' (I'm almost certain it's a type of molex connector) revealed:

http://www.cellpacksolutions.com/battery_Connectors.asp

They'll probably be able to tell you exactly what the connector is and therefore a identify suitable socket, and they're in the UK too.