When friends offer to bring things over or when I'm in the UK, tend to stock up on nutritional supplements (Omega-3 fish oils, EPO, multi-vitamins, vit. B-complex).
Similar supplement stuff in HK can be considerably PRICEY in comparison to what's widely available in say Boots & Superdrug (with frequent Buy-1-Get-1-Free bargains). (Hey, anyone know of cheaper sources here?)
Other things I may miss, occasionally, are:
- the buttery, light & crumbly pastries with dollops of REAL fresh cream, or the savoury cornish pasties, up north
- the clusters of hugely browseable second-hand shops, with varied range of books, old early editions, photos & prints... (HK Island has a couple, but not as extensive, nor as affordable)
- and maybe driving; especially during the height of summer or just into autumn, past freshly-cut grass and hay-stacked gold fields, scented with that distinctive cow-sheep smell... (forgive my rose-tinted sentamentality

)
I really like it a lot here in HK though, and have found just as many things I miss when spending weeks to a month out elsewhere.
While most things are get-able here IF one gets off one's butt to look, can't be so sure of that when in not-so-big a town in the UK.