There are a number of sources for Loss of License coverage in the UK: Haywood Aviation is but one. PM me for alternatives, if you wish.
Secondly, there is no reason why a self-employed, non-salaried, professional pilot cannot insure against Loss of Licence. At least, for "total" loss. If you are wanting a temporary benefit, that might be more tricky unless you can demonstrate a continuous income stream over a period of time.
Any Insurer who tries to escape on the basis that a licence has been "suspended", rather than "cancelled", doesn't deserve to be in business!
My understanding is that most (if not all) Loss of Licence policies cover against the suspension of a licence following a "long term unfitness assessment", OR permanent revocation, on medical grounds. Usually, a 12-month "waiting period" applies from the date of initial suspension. If, at the end of that period, there is little or no hope of the licence being reinstated, the policy pays. One policy I saw contained a further condition that said that the pilot could not apply for the reinstatement of his licence within 3 years from the date of payment, unless with the insurance company's consent and that that, if reinstatement was achieved within the 3 years, the insurance company could, at its option, require a refund of part of what it paid out.