Remember – Do check the lecky statement against your actual reading before she leaves. If you’re in credit, don’t mention it. If it’s got an debit balance (unlikely on 90 p/m) get her to pay her half before she goes!
Do you religiously switch things off when not in use?
Water meter is a must. I got one when I split with an ex, went from £30p/m to £2p/m because I used so little. (They had to back date usage from date I requested the meter to installation). Once in, can you use showers at work to cut down on water & lecky usage?
Only thing I think may be missing – for internet, do you have to maintain separate line rental? Internet should be no more than a tenner, but combined with line rental, can be £20. At that point Mobile Broadband for £15 looks very attractive.
Good luck, you should make it without too much discomfort.