I would personally go for a mid tower. Full tower IMO would be too empty
It all depends what you plan to do in the near future, full bespoke watercooling loop? SLI/Xfire? Need space for HDDs?
In terms of pricing, most of full tower cases are usually expensive compared to mid towers. Whereas mid towers range from £30-£200, depedning on brand and quality.
Again its ultimately up to you to what case you choose, but for me personally, have a look at Fractal Design's lineup, Define S, R5, to name a few - they're pretty decently priced too.