all insurance companys would pay out the 3rd party if your at fault ! if your not at fault your insurance would want to claim from the 3rd partys insurance ! thats what insurance is for, more so to cover other people to make a claim agaist you ....
bellend im a trader and i know insurance inside out, the 20k is the maximum my insurance will pay me out if i make a claim, ie if i own or am in the perssetion of a £200grand bently and i write it off they will only pay me out a maximum of 20k, this 20k figure can be upped at any time, but not lowered untill my policy ends.
also any car i own or am in the possetion of can be moddified in anyway, i do not need to inform my insurance of this,nor does it affect my primium ! the only thing/car/s i can not drive is ammerican cars as this was an optional extra at a cost, i didnt want this on my policy as i will never drive buy or own a yank car.