My winter steed is the same (
Ribble Audax/winter frame).
I used to use clip on half mudguards, but they clogged up the brake calipers. Since retiring, haven't bothered with mudguards and run conti city contacts 28mm tyres. I notice the improvement in ride over the bumps.
99% of my rides are solo rides and being retired can choose the days I go out. I avoid really wet days and will be avoiding frosty days in the months ahead. I have a basic turbo, which I will bring out if we get extended bad weather, but for most times I just use the days in doors for rest/recovery/DIY days.
So my vote would be to get 28mm tyres, ditch the mudguards, only go out when it's dryish and forget the turbo.
Save the pennies for a summer bike upgrade.
Happy cycling