17.5"-18.5" MTB Frame, horizontal dropouts, anything but gaspipe

[Jezston]

Hi, looking for a MTB frame for a project - after something 17.5-18.5" size, with horizontal dropouts (it's taking a coaster brake hub) and of a grade of steel higher than my current gaspipe Raleigh Alaska.

Also handy if you are in London for collection purposes.

Anything you have, let me know!