I guess it depends whether you think the COL crisis is on the supply side (i.e. the cost base in the UK is too high) or whether you think it's on the demand side (people don't have enough money in their pockets to pay what are often global market prices.)
The UK utterly depends on its state-funded public services. Cutting them meaningfully is impossible and we cannot afford them anyway, so reducing taxes is a total non-starter. Diverting demand away from the state sector would be another way, but British class warriors cheered the imposition of VAT on private schools which did the exact opposite; the political will seems to say that everyone should enjoy crap services together.
Net zero is a red herring. It looks like low-hanging fruit in the UK's cost base but I can see with my own eyes that climate change is real, we've got fairly incontrivertable science about it, and more short-termism isn't going to help at all. It's a cost we have to suck up.
One of the biggest costs of all is the price of land, which the government controls not through tax but through the planning system. Torpedoing commercial and residential property costs would be my first priority and if you've planned your entire net worth trajectory based on the price of your house, tough. In the UK, I believe £23 is spent on housing for every £1 which goes into actual productive investment, and that is madness.
Next, I'd have a serious look at infrastructure. I've spent over £400 on parts alone in the last 18 months repairing pothole damage to cars - that's £400 going to factories in Romania and the Czech Republic, rather than to cafés and hairdressers here in the UK. Poor British infrastructure is also one of the biggest causes of poor productivity: put bluntly, you can't be creating wealth when you're sitting in traffic, or standing on a platform waiting for a cancelled/delayed train.
Third, I'd have a serious look at workforce skills, which is the other major barrier to poor productivity (besides British workers simply not working as hard as European or American peers - that's a management rather than government issue though). There's probably something that government could do through the tax system to help with technical skills (which I also view as an industry or business issue, not a government spending one), but equally it cannot be right that senior managers sit around correcting other people's English or Maths when their time should be spent creating value. Literacy and numeracy among school-leavers are really, really piss-poor here, and it is a major impediment to workers getting paid more because often they are just not worth it.