I've bought quite a few items over the past month for making some brass coaches, chassis as well as a NG loco kit. Generally, items by mail order under £20 come with a high (>10%) cost for shipping/postage), but this is low compared with a journey to a specialist shop or waiting until the next exhibition which the trader is attending. Generally I use google to search for specific parts, as many of the traders websites are not easy to navigate - Brassmasters is one of the better ones.
Brassmasters were very helpful, and replied quickly to my email, and the items arrived next day after a BACS transfer had completed. (As good as Amazon and cheaper delivery)
Worsley Works are have also been very easy to trade with - again rapid dispatch for items in stock, and just a week's wait for etches that were out of stock.
247 Developments also supplied by next day (first class post) - online catalogue, order via email and BACS.
Wizard Models, have a fast and easy service through their website but a bit of task to search through, especiallya as many items don't have an illustration.
Branchlines appears a little quirky having no website, but respond quickly to emails and will attach PDF catalogues if asked. They have a load of hidden gems and service, even on larger items such as kits, is very quick.
The only hiccup has been (unusually) Alan Gibson - Colin responded within a day, but trying to get a payment through (by card) has been really dififcult as he's currently changing phone provider, and the voicemail box is apparently full this morning. Hopefully, just a few days to sort it out.
Some of the smaller traders (e.g. Peter Mullen at 62C) balence their specialist service with a full time day job, so things are a little slower - but it's a case of use it or loose it, and we need specialist traders.
Overall I'm really pleased with communications and deliveries in the trade. I try to avoid phoning the smaller traders as they are (hopefully) quite busy enough, and an email is easier to respond to.