Most insurance companies seem to charge an administration fee these days if you make a change to your policy - such as adding another driver, or adding business use - part-way through the year, and that is probably reasonable.
Insurers demand to be told when you make the slightest change to the vehicle specification - including things like fitting winter tyres. In the past, my insurer - when told that I have fitted or removed winter tyres - has simply made a note on the policy without levying an admin charge. However, when I phoned a couple of days ago to report that I had just fitted winter tyres, they tried to impose a charge of £17.50 on me. When I complained, they went into a huddle and then agreed to waive the charge "on this occasion" - with the implication that they would try it on again when I remove the tyres in the Spring.
Have any others had a similar experience? Considering that winter tyres are a safety feature which reduces the likelihood of having to make a claim in the winter, I would take a dim view of the situation if my insurance were to cost an additional £35 p.a. simply as a result of fitting/removing them.