I have a neighbour whose car MOT lapsed 5 weeks ago, its still parked on the road and he drives it sometimes despite so clearly unsafe issues. Am I right in thinking that an invalid MOT invalidates your insurance.
An insurer can't invalidate the compulsory (i.e. third party) element of motor insurance solely because the vehicle doesn't have a valid MOT. So, if your neighbour drives his car on a public road, he can't be prosecuted for having no insurance (unless, of course, he'somitted to renew his insurance policy as well).
As well as the above, the insurance ombudsman has ruled that insurers are not able to turn down claims on the basis of no MoT unless they can show that the lack of MoT was contributory to the incident that led to the claim, Here's one ruling on the point: