Thanks for the further excellent replies. Have been researching and thinking a lot. Have found a fantastically helpful website.
http://www.caymannewresident.com/
Frakked, late Aug/early September is the only time I could move, because that is the earliest I could leave my work on maternity leave (plus adding in all my holiday not taken this year). After September ends, I think I will be too big too fly. Babe is due December 14th. Plus, new intake expats are expected to fly out in Sept and start Sept/Oct.
Seashore I think it's hot all year round, tbf, so it doesn't make much of a difference when you fly out there, though June/July are the most humid. Tourist high season is November- March. In September there is a high risk of hurricanes, and tropical storms. But houses and flats there are built with this in mind. They all have aircon as do cars.
I don't think I'd be racing about much in the heat having landed, but provided I moved slowly and rested lots, I think I could drive round the island with DH, find a place to live and move in whilst in 3rd trimester.
Shipping things: the plan is to rent out our London flat, so we'd leave it pretty much furnished, and just ship out personal effects - linen, cushions, pictures, clothes, some books, favourite pots and pans etc. DH's higher salary would go towards paying off the mortgage faster so we could come back and either move back in to our flat, or sell it.
All flats and houses out there are rented fully furnished. Employers will put you up in a rented furnished apartment for 2-4 weeks whilst you look for somewhere to settle in, buy second hand cars etc. They will also help you find somewhere. they should also put you on their healthcare plan, though I'm not sure that birth would be covered. Babies born to expats on the island can apply for their own passports and US Visas and this process is quite straightforward.I think it would be much easier to search for a flat when pg, than with a babe in arms.
We would have to move house anyway: the flat we own in London is just not suitable to have a newborn in. There isn't even space to put a cot by the bed, unless it is right next to a radiator, the flat has no second bedroom that could be used as a nursery. So whatever happens, I will have to move house this year.
Renting London flat and flying to Cayman is in some ways an easier option than trying to do up flat, put it on market, and sell it before the end of the year (stressful and not very likely. And if we don't sell in time, then how will we market it when viewers come round to find me and a newborn and all the baby kit everywhere?)
And if we stay in the UK, and move home, I am not sure how we could afford a family sized house, with me on mat leave and then probably not returning to work. We would like to have more than 1 and at nearly 40 when babe 1 is to be born, there's not time to hang about. I think it would be easier to be a SAHM, easier to conceive a second (we'd barely see each other if he took another high-pressure long hours city legal job) and easier to get domestic help and childcare on the island.
So on balance I now think, however hard it is to be heavily pregnant/have just given birth and on a small island, it would get easier...I'd be stuck at home when newborn arrives anyway, so why not be prostrate on the sofa in Cayman, than in Hackney? In Hackney I could not afford home help, but over there we could. It will probably be pretty tough wherever I am. But I have got through some very tough times before in my life and I think I would survive, learn to cope and eventually thrive.
Tolalola, thanks! What's it like on the BVI, for legals and legal spouses?