I've just had a good look at mine, which is also MY 2010.

The gubbins attached to the +ve terminal is not the explosive battery disconnection device, which was fitted to earlier cars. It appears to be a very simple mega-fuse, protecting the power supply to alternator and starter motor. In addition to the main cable going through to the engine compartment and off to alt/starter, there are two large dia cables going off to the nearby fuse box (behind the battery) and another very thin wire going goodness only knows where.

The mega-fuse sits at the end of the battery, at the level of the +ve post and a little below. It prevents fitting a longer battery without making some changes to how this fits. This is in contrast to earlier vehicles, where the battery disconnection device sat above the battery and didn't get in the way.

The arrangement is really quite different from earlier vehicles, although some of the same principles will apply. Advice to open out the clamp sufficiently to make sure it seats at the bottom of the battery post is good. Tapping it with a mallet might be a good move, but I can imagine access must be a bit tight. Panic about hitting a bomb with a hammer are simply not relevant as there is no 'bomb' present.

They say a picture speaks a thousand words.....

Item 2 is the cable to alt/starter
Item 3 is the megafuse
Item 4 is the transit relay (and therefore removed at the pre-delivery inspection)
Item 6 is the battery management system
Item 7 is the battery to earth cable

Click image to enlarge

Thanks for all the advice chaps.
I'm going to have another go at it this morning.

I guess you may have already resolved this, but if not this may help. Are you fitting an 020 battery? if so I seem to recall a similar problem when fitting mine. Although the battery fits the tray (just) the "positive side" is too close to the bulkhead on the right of the tray, this caused the Fuse carrier on the lead / terminal to rest on top of the bulkhead and lift the terminal slightly off the post, it looks like its on but it won't tighten! To resolve this I had to cut the mounting lug off the bottom of the left hand side of the battery which then allows the battery to be pushed over perhaps 6mm and gives just enough clearance. I suppose it may be possible to place a packer under the battery?
Hope this helps.