Hi Andrew,
Thanks very much for taking the time to do this, much appreciated.
Huge advance and I've learned alot more from this than Googling in the dark.
I've noticed there's a mixture of formats for page ranges as you can see from below:

Before .................................................. ........ After
average variable (AVC) 108, 305 < > average variable (AVC) 108, 305
external 41–3, 164–5, 175, 186–8 < > external 41–3, 166-7, 175, 188-10
long run 113–14 < > long run 115-34
marginal (MC) 105–6, 110 < > marginal (MC) 107-8, 110
private 41–2, 186 < > private 41–2, 186
short run 106–9 < > short run 108-11
social 186–7 < > social 188-9
credit 16, 205, 206, 215, 258–61, 308 < > credit 16, 205, 206, 215, 260-81, 308

If there's for example 186-8 then After should be 188-0 (to keep the current format)
I have another question, your code includes
This is a regex notation, but there's no mention of a RegExp object. How does that work?
Thanks for all your help