https://www.rocketrailways.co.uk/
Quote from their website:
Here you will be able find something to complement your model railway layout. We buy and sell OO Gauge, N Gauge, O gauge, G Gauge and indeed any other gauge. So whether you are looking to sell your items, trade or buy we hope you enjoy our website. We started this company when we saw the enjoyment of families when they were together creating a model railway layout. Its a great hobby to bring the family together without the need of the TV!