Hi Mary,
I've just gone through all this with my 2. Am going back to work in September and, after looking into CM v Nursery, I have decided to send both of mine to nursery. I really thought I'd go down the CM route as Evie will just be 6 months and she'd get more 1 to 1 care there until I realised that that'd be the case in a morning but in the afternoon there would be her plus 4 three year olds which put me off somewhat! There weren't many CMs in our area that could take both of them and do Joe's pre school pick up too which also contributed to the decision.
You should find that whichever way you go the carers hours will be flexible and they'll work around you to an extent. I found our local childcare information service really helpful, from the sound of it you're in Hampshire so try 01962 813887 or look at http://www3.hants.gov.uk/childcare/ for more info on carers in your area. The Lancs childcare service sent me a brilliant booklet with top questions to ask prospective carers and ideas on what to look for. It's worth knowing that all CMs and nurseries are Ofsted registered and you can read their reports online. Whichever way you choose to go they should be happy for Isabelle and you to spend some 'settling' sessions with them so that you'll be confident that she'll be happy and settled once you're back at work. My OH was quite happy to let me sort Joe and Evie's care out too, I think it's a man thing!! Mind you, I think I'd rather it was that way as I'm not sure he'd have researched it to my high standards lol!!
For what it's worth, I wouldn't leave either of mine in a house where there was a Rottweiler either!
Hope this helps somehow, sorry it turned into a bit of an essay!
Zoe