RBS owns the Direct Line Group (Direct Line, Churchill), but is in the process of selling it. That's the only really big bank-insurance operation.
HBOS/Lloyds owns a relatively modest household insurer and a couple of medium-sized life insurers.
Barclays and HSBC each have very small insurance operations, unless I've forgotten something.
None of them own major brokers. None of the major overseas banks have big UK insurance interests.
Of the big names in the non-life insurance market, Aviva and RSA are independent listed companies, Axa is owned by a French insurance group, Zurich by a Swiss insurance group and Allianz by a German insurance group. I don't think there's any bank money in Lloyds.
I'm less familiar with the life insurance world, but both the Pru and L&G are independent listed companies. A lot of the old companies have been merged into Resolution, a UK partnership. There are also companies owned by Aegon, a Dutch insurance group and ING, a Dutch bank.