Faster, stronger, lighter... for under £1,000

yes, +1 for training - you can spend a LOT less than £1000, lose 10kg body weight, and suddenly you will fly up hills!

Maybe the planet x cx bike or the flat bar version.
We are about the same size and weight and have a similar commute and I use a ridley cx bike.i wouldn't say it was significantly faster than your genesis.i would buy some better wheels and run tubeless that will save weight where it counts and keep the bike you have

"Faster, stronger, lighter... for under £1,000"

Sounds like a good training plan

My first question would be what's wrong with your current bike? The CdF is lovely and sounds perfect for the commute you do.

If you ride it harder it'll be YOU that get's lighter and faster (rather than the bike and your wallet) and that's got to be a good thing. I used to do a similar commute (on a Croix de Fer) but found that the towpath, whilst away from the traffic, was slowing me down: all those dogs, runners, drunks etc to watch out for. I switched to a busier route where I could properly put the hammer down and also take in some hills and that had the biggest effect on my fitness and speed.

Like you that then lead to me wanting a new bike but without the towpath requirement what I wanted was completely different (I went for a Ti road bike).

If you can afford it keep the CdF as your winter do-it-all bike and get something more road-specific for longer, faster, hillier rides. I really miss my Croix de Fer and wish I'd found a way to keep it.

Your preference for "retro" looks sounds like steel is what you want. Harder to get something very light for under £1000 in steel than in aluminium or carbon. You could do worse than stick with Genesis and the Equilibrium. Now is a good time for deals so you could get a higher spec bike at your price point.