I have Lumenition Electronic Ignition on my car and the knurled nut definitely moves the ignition timing whilst running as evidenced with my strobe light.
Blatant profiteering on the part of HMRC, bet they didn't give a VAT refund when the car left the UK, so why now should it be due a second time? (Acknowleding that as it probably predates the introduction of VAT purchase tax was more likely to have been levied)
Each to his own but I've always found EPAS to be a bit artificial in every modern I've driven. Given the CDD hydraulic option is listed as £1400 I'd be beating a path to their door if I was ever in the market for PAS for my TR6