He's in the UK, he will have lots of time for sharpening, probably has to fly for several hours to get to a decent hill...
Back on topic, in additon you should get a gummy stone, which is like a rubber pencil eraser with some grit in it, you can use it for deburring and for detuning once you have sharpened. I like to use it intead of the diamond stone, it's more forgiving.
You also should get a magic marker. Before you sharpen your board you paint the edge with the marker and then as you pass the file over the edge to sharpen it you will see what area has been sharpened as the ink is ground away by the file.
Note that deburring and sharpening consume your snowboard by grinding metal off the edges so you should sharpen when you need it, not every 3-4 days, which may be unnecessary.
You won't need to deburr much if at all unless you are hitting rocks/riding where there are rocks/gravel in the snow. You won't need to sharpen if you are riding in soft snow, ice is what dulls your edges (and is when you need sharp edges).
So if you were to go riding for a week in nice soft snowy conditions your board would likely still be sharp (and it wouldn't matter if it wasn't sharp in soft snow anyways). If you were riding in really icy conditions you likely would need to sharpen sooner.
Learn to test how sharp the board is by drawing your fingernail over it, if the edge scrapes a little layer off your fingernail then its sharp. If you get your board sharpened by a shop you can test on a sharp board or try this on a new board, ask the salesguy if it comes already sharpened (most do).
If you're the sort of person that likes to do their own maintence I suggest getting an iron, brushes, scraper, etc. and then you can wax your board yourself. Most people learn to wax first and later start maintaining their own edges, and lots of riders only get their edges done by shops, they worry that they'll screw up their edges, whereas waxing is pretty hard to screw up, and permanent damage from waxing you almost need to deliberately have to try to do it.
So would you recommend I just get a gummy stone, so I can de burr if I need to (good chance I'll meet some icey conditions), then worry about sharpening properly next season if needs be.
I noticed that arbor have detuned from the factory so not worried about that any more.