Health cabin's shipping to the UK is brutal (about $9). Sourcemore is usually more like $4 or $5. IME they both come pretty fast when in stock (8- 10 days ish), but pre-orders... well I have hung round for months before now.
I've used SM more often tbh, and they've been pretty good when things have gone wrong. Once they sent out a replacement straight away, another time they made me jump though a few hoops but replaced eventually.
Never had trouble with Health Cabin, so I can't say.
The very best service I've has has been from UK companies on here like manabush and prime vapes.