Finally, something I'm genuinely qualified to comment on !!
As this is what I do for a living :
You want 40mm not 32mm for a start.
Howdens = expensive
Worktop express are my suppliers of choice. Their product is good, delivery excellent and the items are transported well (well protected from knocks)
Re oiling wooden worktops, don't listen to anyone telling you that Danish oil works, it's crap. You will need to constantly re-treat your worktop and it will still stain if you leave water on it. Not only that but treatment takes ages (drying)and you need several coats from initially - realistically several days worth of fannying about.
Professionals worktop treatment of choice is EZ-oil by Morrells. This product will give you a mid sheen (getting glossier with repeated coats - especially if they are thick coats left to "flow" to a smooth finish.)
EZ-oil dries very quickly. You can put several coats on in 1 day.
Important - do not forget to oil the underneath and any end-grain cuts (inc cut-outs for sink and hob) before you fit !! You'll never be bothered to get to it once it's in and it is important if you want to avoid warp or bow in the future.