I can reccomend the 1mm thick Chinese el cheapo diamond plates. They cost about 3-4 quid each and do well for bevels. Grades from ~120 up to 3000 are available. these are about 7x3" in old money, larger are available if you search. The thin plate is quite stiff; if it bothers you stick it onto something flat with polyurethane glue. Look on Ali Express or ebay. Ali Express now charges for VAT so prices gone up a bit for UK delivery (another Brexit minus).
I grind ~25deg on a wet wheel, and sharpen 30ish on the diamond 1000 or 1500 grit, and finish about 32-35 on a fine 8000 waterstone, kept flat with wet/dry on a glass plate. When waterstone worn out, will finish on abrasive film on the glass. This should last well, as last sharpening takes only about 6 strokes.
To flatten backs, use abrasive film on glass; you don't do it often, so film lasts. Also use DC's ruler trick (google for details).
No need to spend big money on a single stone!
I grind ~25deg on a wet wheel, and sharpen 30ish on the diamond 1000 or 1500 grit, and finish about 32-35 on a fine 8000 waterstone, kept flat with wet/dry on a glass plate. When waterstone worn out, will finish on abrasive film on the glass. This should last well, as last sharpening takes only about 6 strokes.
To flatten backs, use abrasive film on glass; you don't do it often, so film lasts. Also use DC's ruler trick (google for details).
No need to spend big money on a single stone!