I'd put the Capital slap bang in the middle of the country!
Have a cracking public transport system - rail in particular!
I'd not have most of the land and wealth given to so few people
There wouldn't be a monarchy
water, gas and electric would be none profit making organisations!
lots of good quality social housing
lots of good open spaces
I'd make sure systems were efficient and not built up into the huge, wasteful, ridiculous things they are now that nobody wants to take an axe to because they have been established for so long and it would cost a fortune to sort them out and even though they are haemorraging money, the thought of actually doing something about it makes people threaten to strike
I'd make sure that there was actual industry in the country with actual, real things to sell so we could trade with the rest of the world and we wouldn't have to import practically everything because we've closed down most of our factories
There wouldn't be dole as such. Everyone who was physically able would work. If they couldn't find a job then the state would pay them a wage in return for work. In hospitals, parks - so many things. They'd have a choice. But choosing to do no work would not be an option for people capable of work.
Vulnerable or disabled people would be much better supported.
And there's loads more, including probably a novel on the criminal justice system 