Cut back on the leisure spends! Over £100 a week, plus your Prime/netflix subs on top, is a lot, and all of it's discretionary.
If you can pay the car insurance in one hit instead of instalments, you'll save a few quid. And make sure you use a comparison site when it comes to renewal time, to get the best deal. Could you manage with just one car?
I'm jealous of your council tax. Mine would be almost £2k a year if I didn't get the single person discount, and it's only band C.
You could find a cheaper internet provider too, once you're out of contract. You haven't mentioned phones, if you've paid for your phones, look for a sim only deal.
Is Homeserve worth having? We looked into it years ago, and decided it wasn't. All our bills over the lifetime of our boiler only came to a few hundred, a lot less than Homeserve would have cost over the 19 years we had that boiler. My current boiler is less than a year old, is guaranteed for 13 years and all I have to pay for is an annual service.
Shop around for your house insurance, too. Mine, combined buildings and contents, is just under £200 a year and that includes an additional premium for 2 valuable items.