OneMoreTime23 is correct that it might be indemnity rather than public liability, depending what you're doing.
I'm not an expert and that's what you want, but there's plenty of common sense guidelines for the level of return you're talking about.
OneMoreTime23 is also correct about insuring your car for more than social and domestic use, especially as you're providing written evidence that you are using it for business, to HMRC.
The later will probably ignore it and allow your mileage, but if a serious accident happened an investigation would show you as uninsured by omission. There are things you can wing it on, and things you shouldn't. That's one of them.
The additional insurance is a tax deductible expense.
Business bank account charges (You need to set up a business account not try and use your personal account- will be closed if discovered.)
Generally food is only tax deductible with overnight stays. It's also a potentially sticky area that gets scrutinized.
There's something called the "dual purpose" test. If you had a personal reason for incurring the expense, even if you also had a business reason for it, then the expense would be disallowed in its entirety - unless it could be accurately split between part that was for business and part for private.
So you had to get lunch because the meeting was over lunch time? The lunch is dual purpose, you both needed to eat regardless of the meeting, your business purpose falls under entertaining, so the lunch bill is disallowed.
Claiming percentages for using your home when you're one day a week using your kitchen needs to be offset against do you need permission to be using it? Do you need to pay charges for running even a small business from home? Are things like domestic rubbish collection affected? Is this small offset worth the trouble it can bring? (HMRC tax rules generally ignore other rules that don't affect them, but a grabby council can use your SA evidence to fine you for disposing of tiny amounts of commercial rubbish in your domestic bin.)
You can't offset fines or parking tickets.
You can claim a small portion of CT, but may run into problems from your council running a business from home once highlighted.
A small portion of your internet, heat, water, light, rent, mortgage, CT, can all be claimed if you want to do that maths.
If you wanted to claim your kitchen use you'd be looking at say in a 2 bedroom house: taking a 5th of your heating/lighting bill, (no of rooms) then a 7th of that, (days in use) then 1/2 to 2/3rds of that. (time actually used) If they want to get sniffy, it becomes a percentage of that percent as it's assumed you have basic heating, so it becomes a small additional amount, whereas the electric usage for additional light is clearer.
Or a much easier answer is claim the £6 pw flat rate use of home allowance which doesn't require receipts and evidence to prove.
A mobile phone wholly for business use, absolutely, (small amount of domestic calls is accepted) or it's a percentage (inc any insurance) based on how much use is business vs domestic.
Computer, memory sticks, increased ram etc, absolutely. Printer cartridges, office supply's absolutely. Costs for Zoom, computer programs and packages needed for your business, relevant associations, further training, publications, are all deductible because they are solely for business use.
That doesn't mean that things like feeding, wining and dining, or that little black dress (even if it does mean you got the contract and you don't wear it for pleasure) are allowed, because the rules got written and re-written to lower abuse of them.
Having read your other thread, the advice to get an accountant or tax advisor is sensible, they earn their money, and are a deductible business expense, as are legal advisors, solicitors etc.
If you don't, then follow the general rule of thumb around the sticky areas.
The amount of time spent wrangling over if a coffee should be treated as tax deductible or not, is generally better invested in growing your business. HTH