There are very few defences an insurer has under the Road Traffic Act. One of the few defences is using a vehicle outside of the use permitted on the Certificate (so, for example, if you are insured just for social use, but have an accident while driving for work, the insurer has a valid defence. They will still need to pay the third party, but they have a right of recovery against their insured).
"However an insurance company will use any sort of illegality to reduce or refuse a payout." If TTT is referring to payments to third parties, he is wrong - they can't. If he is referring to own damage, he is also wrong. This would suggest if somebody hit a third party up the backside while speeding the insurer would reduce the amount paid out for the own damage. This would be a breach of contract - it simply would not happen.
If there is a 'drink/drugs' clause in a policy (which is extremely rare), then in the event of an accident the insurer is only responsible to the third party - not for the own damage. If there is not such a clause, refusing to pay for own damage would be a breach of contract.
An insurance policy is a misnomer - it should more accurately be described as an insurance contract. In consideration of the insurance premium, the insurer will pay to the extent the policy allows them to pay. It really is as simple as that.
There is no 'small print' in consumer insurance contracts. They are now extremely easy to read - anybody who reads one and does not understand what they are and are not covered for must, frankly, be a bit dim.