i converted my 1.3 pop to 1.6 rs turbo spec in 2005, and in its time was insured with 2 different insurance providers, neither of whom requested an engineers report

i simply declared the modifications to them, and of course the DVLA for taxation purposes, and all was good

infact the DVLA informed me that 99% of the time, and engineers report is not deemed necessary for increasing capacity, more so for those decreasing capacity and power, so those who could potentially be trying to reduce their insurance and tax. would be a fool who lied about increasing capacity and power in order to cost themselves extra running costs lol

so long as its declared, all should be well, mine was never an issue