Its practically impossible to go solar only off grid in the UK.
To go offgrid you need most of four things, possibly all combined
1) A really massive array, as you say winter generation can be down to a very low % of theoretical array size
2) Off grid power generation, so a petrol/diesel generator is most usable, which is what most offgriders have
3) A will to be very low usage potentially for some time, ie just enough to survive, no loads of washing and tumbling if generation is a trickle
4) An alternate source of warmth, log burner, coal fire etc
Modern batteries are now typically 5000+ cycles over 10 years warranty (or more cycles (more is pretty much irrelevant))
Eg
https://batteryfactory.co.uk/products/givenergy-9-5kwh-li-ion-battery
They use LiPo4 now
If you can get on a cheap off peak tariff (Octopus by far the best in market right now) then you can charge for less than 10p per unit over night.
If your battery gives you somewhere like 70% plus of your daily usage even in winter you will have days with grid independence, but not many.
Spring / Autumn you will likely be basically neutral, with summer generating real excess. (Assuming a suitable array for your consumption)