Garden lyme

Vinny will know, I'm sure.
I haven't a clue. There's a bag of 20 year old lime in my shed and I still don't know how to use it.

Thanks for your faith in my abilities Veggie but in this instance I am not much help!  My Uncle had a smallholding on acid soil and seemed to manage ok without liming? I did use magnesium limestone (crushed dolomite) on one of my plots, particularily in the areas I was growing brassicas.I believe the brown Magnesium limestone doesn't cause potatoes to 'scab' like the white garden lime does?
As an aside, in my first garden I ever had I burried loads of plasterboard from the house renovation  and covered it with soil. I grew the best broad beans I have ever grown on top of plasterboard.
I personally would go with the RHS recommendations and liberlly apply to the surface,dig it in then re apply? You could of course interogate your immediate neighbours and see how they managed?