Winter training with power

It would be highly unlikely you could overtrain on 4 rides/week.

There's never a bad time to do intervals, just there are more appropriate times to do a given volume of high intensity work. If it's L4 work or below, you can do that pretty much any time. Nothing wrong with a smattering of L5/6 either, provided it's not a dedicated focus on that stuff.

Maybe try one of our training plans?

Likewise I'm in England. I've always reckoned the Sunday club run is pretty dodgy in terms of training value - they often comprise dead miles sitting in, mixed with hammering up hills, and bisected by bad food in a steamy cafe and a chance to share every germ in current circulation. Okay, I'm a miserable *** but you get my drift.

If you can only get out at weekends then I'd think about what sort of rides you do and who you do them with - maybe mix social rides with solo rides, or find some like-minded riders for company; keep the steady miles steady.

If you're happy to crank up the turbo tthen intervals through the winter are useful - it's just a question of what to do, when. I do one set of 2x20's each week at threshold, all the way through. In a month or so I'll start doing some lower-cadence intervals to work on strength/force. Come January I'll start doing a sprint intervals regime that initially just works on leg speed, and by February I'll be starting to mix in vO2max intervals too. So there's plenty of variety and by the time the first serious races are a month or so away I'm on to full-on sprints, hill sprints and 1- and 2-minute intervals.

Having said that, I did take a full month doing next to nothing (one steady ride a week) following the end of the last season. I'm sure I've lost much of the top-end fitness, but the basic aerobic fitness doesn't seem to have vanished, and the aim of the winter is to build on it, rather than simply avoid losing it. I'm about the same age as you. Be bold!