Online Instrument Dealers
Most specialist brass shops have websites and will sell by mail order. Here are a selection of links to the second hand pages of some of these dealers:John Packer
Hayes Music
Prozone Music
Band Supplies
Phil Parker
Dawkes Music
Duchy Brass
First Brass (Broken Link)
Trevor Jones Trumpets | Cornets
The Wind Section
Trevada Music (trumpets)
Trevada Music (cornets)
Once Loved Musical Items
Reeves Brass (Broken Link)
Gerry Birch Music Services
Bexley Brass
Musical Money
Windblowers
Headwind Music
Play it Again
Sharon McCallum
Hogan Music
Woodwind & Reed
Nightingale Trumpets
The Music Cellar
Geneva
AT Brass Repair
Hobgoblin Music
2nd Wind
Non-Specialist Second Hand Dealers
Cash ConvertersCash Generator
Ebay
Here are links to searches restricted to results from the UK:Trumpet
Cornet
Classified Ad Sites
Gumtree, will return national listings so you will need to narrow it down to your area.cornets for sale on Gumtree
trumpets for sale on Gumtree
Physical Auctions
You need to pay buyers premium and they won't usually post items, you need to be able to collect. There are a few online bidding services used by auction houses. Here are some of them.the-saleroom.com
ukauctioneers.com