Could I have recommendations for a decent 4 season sleeping bag?
I'm a little bit allergic to down so hoping to find a synthetic bag that's warm enough for trips into the UK hills and mountains during winter.
Will be hiking so bulk not quite such an issue as when bikepacking.

Have a look at the MH Lamina range. Lots of choice and can often be found at a good price.

What he said about -2 ish for £100 ish ( sales) ,@800 Grams ish
I don't think you can do any better in the balance between price weight and warmth

I once had an MH ultra lamina 0, crazy small pack size for such a warm bag, I don’t think they make the ultras anymore and it’s something I regret selling

Not sure if a quilt appeals but the Climashield Apex insulation is very good, I know Wiggys make Apex bags but I think they’re more aimed at arctic forays

I’ve got a Mountain Hardwear Lamina 0 in the cupboard upstairs that I’m not using. Not sure if it’s the regular or long version, I’d need to check. Pm if you’re interested.

Sounds great! Have pm'd you.
I'm only 5'11 so guess either length would be fine.

Sillybigfella. Can I just check you received my pm? I've not heard back from you.