I was listening to a programme on BBC4 on Saturday morning & there was a discussion about the attitude of a particular major insurance company towards modifications. The case in question concerned a claim made by a car owner, following an accident, where the IC had initially not only refused to pay out but also cancelled the policy because their assessor had reported that the car had 'none OE parts fitted'
Eventually, when the owner provided evidence (which took a while to compile & during which time he was without the car) it became apparent that these components were available from the car maker as options & manuf. to OE standards, the IC relented & re-instated the policy.
I don't have to practice what I preach because I'm not into mods. but read a lot of posts on this forum from proud LR owners describing the mods. that have been carried out to their pride & joys, so do be aware of the need to inform your IC because if you have to make a claim .......

i c will try any thing to get out of paying up

EU is trying to bring in regulations and has done in some countries Spain for one. That if non standard parts are fitted that do not conform to the vehicles original spec it will fail the test. This happened to my lads father in law who lived in Spain and imported a Merc 4x4. He had to remove window tints and would have had to have had Merc tinted glass fitted by a dealer at some astronomical cost and have them added to the cars spec to pass the test. Also had to remove the side steps and have them fitted at the dealers and added to the spec even though they were genuine Merc steps but fitted privately after market. This was supposed to be brought in to the UK by this year i think but apparently has been resisted by VOSA. It would virtually shut down the after market parts trade.

Some places are shocking. California and parts of Aus I know are, any part, even an air filter has to be done at an approved dealer or it fails. So much so that I know folk who swap whole bloody engines when it comes to "MOT" time.

Every single modification, restoration or upgrade I have done has been reported to my IC over the phone, then I email them a full list each year, along with what it does, value and any other impacts. Flux have been great, never increased my premium by as much as £1.

Direct Line on the other hand where utterly useless and had no idea what a roll cage even was, eventually went down as 'bumpers for the roof' :S