Training!
A bit late now to train for the Mersey, but it won't do you any harm, as long as you don't overdo it and are well recovered before the big day.
Maybe you and Charlotte could set up some turbos in your new garage?
That seems like the best option given that you are surrounded by traffic lights.
You can then start doing all the different trainig excercises which have been mentined as well as pyramids and a few good steady efforts.
You really need to try and make it as enjoyable as you can. I wouldn't bother doing long low intensity turbo sessions because you'll most likely get bored rigid. Roads are much better for long rides and getting the miles in. I'd only do turbo training for the high intensity stuff. You probably aren't able to ride flat out for very long as it is, so at the moment you'd be spending well under an hour if you're trying hard enough. An hour is plenty if you put the effort in. If you get really keen, then an hour twice a day, but that would be some time away for you.
I wouldn't turbo in the home unless you are pretty sound proof. It's not just the noise of the turbo, but also the heavy brerathing. Put some mats or plastic on the floor if you do some turbo training in your home. You'll get very sweaty. Worth protecting your bike from sweat too.
The most important thing is to enjoy it or you won't keep at it. Make it part of your routine and don't miss a session without good reason. Even if you don't feel like it, you'll most likely be OK after a warm up.
Apart from that. You can find out different training methods if you look. Variation is good. It makes it more interesting and keeps your mind fresh. Try out new things and experiment.