UBI is easy to set up and maintain.
Simply use the money that runs the welfare state, and give it to every citizen over 18. Bosh, job done.
If everyone gets a UBI, there is no need to have council/civil workers to admin the welfare state.
The bureaucracy costs of means testing, checking, interviewing, and actually filling the applications for benefits comes surprisingly close to giving everyone in the country £14k per year.
Then simply remove the tax free allowance, from earned wages, keep the current tiers of tax, and boom! UBI for all, with no additional cost to anyone.