Looking to change the battery in my S1 Elise, but I notice that someone has previously removed the breather pipe, so I don't know where it should be, or what form it takes...

Anyone got any ideas?

Regarding battery breather pipe you should find two small holes at top of battery. Make sure one has a plug in, remove opposite plug and fit in small diameter washer pipe or similar.
Make sure the pipe is long enough to drain any stray acid to the ground safely etc. This will protect car internals from acid damage.

Thanks Chris - when I removed to old battery I actually found the pipe already there - just not connected.
Who ever replaced the battery last time obviously forgot to re-connect it!