We could literally replace our entire fossil fuel power generation with green nuclear power for the budget it already is, that would be a monumental achievement, an environmental milestone, and protect our energy supply from nefarious countries, that's forward thinking, not this rubbish.
The problem is, you would still need to improve transport links, preferably in a manner that removes as much fossil fuel from the mix, and at the same time can transport very large numbers of people and material.
We could wait for electric aircraft (which would still have all the limitations and more of fossil fuelled ones), or build yet more roads and the chargers etc, or we could do what we should have been doing 30 years ago, building new fast tracks so we have a rail network that can compete with the motorway network*. We've got hundreds of thousands of people a day (if not a million or more) trying to use rail lines that were built for a fraction of the number, to get to work from increasingly long distances as the price of housing in major towns means that "affordable" housing is moving further and further away.
We keep building an extra lane onto the M6, extending the M25, building new bypases for the road network that maybe last 10 years before we need to build another one as the road capacity is now maxing out on the north side of the town rather than the south...(seriously in the last 25 years my town has had something like 5 bypasses built**). At the same time we've basically only built two new long stretches of trainline in the entire country, despite the fact that a train can carry hundreds of people safer, more cleanly, and in a way that means they're able to do something other than sit looking at the car in front of them for the entire journey.
We should have at least two lines (either way) going along similar routes to all the motorways and at least one line going near most of the major A roads, with the interlinks that the road system takes for granted to allow for disruption to be worked around so routine maintenance on a couple of miles of track doesn't completely shut down the rail network for tens of miles and require you to get on a bus.
We could, and should be doing both, there is nothing that says you can only have reliable power, or new trains, and part of the problem the UK has had since WW2 is that increasingly no politician wants to invest in infrastructure (or anything else) that they won't see the benefit of before the next election, let alone anything that is potentially unpopular for some of their local voters (regardless of how much it'll be popular with the rest of the country, or how desperately it's needed), which is why we get a few miles of "bypass" built that might be done in 3-5 years (if you're lucky) but works for just long enough to get them through an election cycle before the traffic has built up again to the point where the bypass needs a bypass.
It's the reason we've got a power system that's failing because no one has wanted to build new stations, even as the old ones are being shut down, it's the reason why we're pumping raw sewerage into the rivers and sea (undoing 50 years of trying to get some of the rivers to the point where they've got actual wildlife in them, not just floaters), our rail network is basically worse than almost any other "first world" country with the exception of America, and why our businesses tend to be behind the likes of German in terms of productivity as it seems no one in this country wants to invest in things.
*IIRC one of the reasons we don't, is the guy that basically made the decisions about investing in the 60's, was from memory involved in road construction...
**Largely because no one seems to have ever considered that there are only two roads going on way through the town, and one the other...so the town has pretty much doubled in size, all the amenities/services are still in the centre of the town, but only the road that runs through the centre has been there since the 1400's (so one of the bypasses basically lets you take a route that's about 10 times as long, go all round the outskirts of the town, a trip of several miles at 60-70mph, to avoid about a quarter of a mile at the centre of town).