I know that thread has drifted a bit, but if you're looking to keep a battery on a "tender" floating system, I would recommend one of these.
They go directly onto the batter and the charge end can be hidden up front so you don't have to remove the bonnet to gain battery access. They're also fused with a 10amp fuse for safety.
These are available and most any bike shop here in the US for around $15. They're available on eBay also. I'm sure UK bike shops have the same harness. They're usually a couple foot long so routing them is not a big issue.
These have your normal 2-prong plug end that most all tenders use.
