A quick scan of PC World (
https://www.pcworld.co.uk/gbuk/compu...ers-889-c.html) would indicate that your size requirement will mean a Windows tablet - Android tablets seem to be all in the 8"-10" range. So you'd be looking at Surfaces or similar (
https://www.pcworld.co.uk/gbuk/windo...-criteria.html). Unfortunately, we're a Mac shop and we both run iPads so I can't give you any advice on Windows machines.
Price-wise, you're looking at £199 for a LINX 12X64 12.5" Tablet & Keyboard - 64 GB to £2419 for a MICROSOFT Surface Pro - 1 TB.