Don't bin it! I've ordered a load of batteries, I'll post details soon about sending them to me for repair Special OOF prices too
Fair enough mate,but the pain in the you know what to change them is for very little gain....but thats just my opinion... 
Do either mate, but definately do one - don't leave it connected to long how it is.
I would have a look at getting the batteries replaced if you are planning replacing (depending on cost), but I think vauxhall quoted me about £60 for a new one.
I believe the unit is sealed and the batteries are soldered in.
I left mine disconnected and threw the old one as there is still a horn when the alarm sounds. However, it is a simple job to replace and while I would'nt shell £60 out for a new one, I might have had the old one repaired if it was an option.
If you leave it disconnected, I would make sure you cover the connecter block well with insulation tape, before tucking it away.
