Jolls re: the job. I obv don't know the details but, as you have said your job security -and I assume mat leave entitlement etc - will not be affected then I would say go for it.
If it's a step in the right direction and the job appeals to you. Some folks would probably say to consider which would be better after mat leave, for part time working etc. But I'd say that 6-12 months (or however long mat leave you take) is quite a long time and a lot can change. From reading threads on here, a lot of women seem to be very frustrated when they go back to a role and part time work (FT but trying to fit in new commitments). You might change your outlook, colleagues may leave, all sorts can happen.
I guess the point I am trying to make is Carpe Diem, seize the day. If it's the right thing for you to do for the next 5 months or so, then do it.
That's just me though. My control freak super organised SIL manoeuvred herself into a role she could see would work on a PT basis before she even got upduffed.