Plastic soldier company are selling off lots for not a lot...
https://www.theplasticsoldiercompany.co.uk/shop/sale-items/
I have these myself, and you can't fault the price range. The miniatures are fairly decent, and can be quite scale agnostic - meaning a miniature played as a destroyer one game, could easily be played as a cruiser or a light corvette another game. They paint up fairly decently, though the detail is a little on the shallow side, so washes aren't so effective on them. I think I gave £10 for a big bag of 30 odd ships, which means you can quickly and easily build up a fleet.