Moving house (exchanged) in 2 months but need car insurance

I’m moving in 2 months - how do I find what insurers will charge at the new address?

I just bought my first car at 32 (so no no claims but I’ve had my license for 14 years.)

I’ve got quotes from £450+ and like the t&cs of aviva at £516... but when I checked with my new address it didn’t even come up as an option under £1000. In fact cheapest is £850 for the new address.

I’m moving from an apartment block with locked compound to a semi detached house with a garage, probably in a higher crime area although they are likely similar.

Where the other quotes so high because I’m not registered to vote at the new address yet or am I just moving to £400 extra crime a year? Is there any way I can find out what I’m letting myself in for? I sent an email to the help team but no where is taking calls. Is it better to get temporary insurance and then annual when I move? (But council will probably delay registering to vote process so might not be cheaper.)

Help!