It's easy to do a valve job by yourself, but I think you're confusing a valve job (where you pull the head and reseat the valves) with adjusting the valve lash, which is also easy. Unless your valves are making noise, I wouldn't bother.
Adjusting the valve lash takes all of 15 minutes and is really easy. There's a DIY here on the site for it.
You should not need a new valve job unless you have bent your valves. You have to pull the head, disassemble the valve train, clean the head, lap the valves into their seats, clean the head again, lube everything up, reinstall it, and then you're done. Good luck with two things:
1. Finding a shop in the UK who will even work on a D17. I couldn't and I lived there for 3 years.
2. Paying the labor rates for said mythical shop to do so.
if you know how to take the valve cover off, use a feeler gauge, know which piston is at tdc at any given time, know where the intake vs exhaust valves are, where the adjuster nuts are, and how to turn the engine manually, should be piece of cake to adjust the valves. i dont even think it would take all day.