The likes of Church sales are excellent for buying plants, because they've usually been donated by keen gardeners who've raised them carefully. Ditto plant stalls at charity garden open days. Be wary, though of car boot sales, where "plants" are sometimes unrooted cuttings stuck in a pot the night before.
I've never had problems with coriander, either in Aberdeenshire or in Caithness, and neither place is its preferred environment! Fitivver, anyone having problems should try Cilantro, commonly known as leaf coriander, with virtually the same taste. It's hardier and less fussy, and grows like a weed.
And ellsie, like Kay says, pop over to Chinwags, or even drop into Ruggies. This wee board is a long way from mainstream BritishExpat
. (And if you're not a has-been or wannabe expat, nae worries hen. Me neither)