I'd PM JazzCNC and ask what specs he can build for you in that price range. I'd wager it'll outperform the stepcraft by a decent margin.

Personally i'd take £100-300 of that budget and buy a dedicated 3D printer off the shelf - something like a Creality Ender 3. Don't try to combine the two things into one device - they require different things, its like buying a lorry because you need to move things around, and then taking it on track days because you also want a fun car. The 3D printer needs high accelerations for a lightweight print head and doesn't need to absorb any cutting force. The router needs to be big and beefy to cut through things and to stay as rigid as possible, typically at a much slower speed.