Yes - the license awarded to TrustMark by Government covers all of the UK.
TrustMark operates under licence from BIS (formally DTI/BERR). It is run by a Board, which includes representatives from consumer organisations, scheme operators and independent observers.
TrustMark is operated through the small amount of fees it charges its scheme operators for each registered firm. So the scheme operator is charged, not the registered firm, and it is up to the scheme operator whether and how to pass on the cost as part of its fees. However, we expect that in most cases any extra charge for TrustMark registration will be small.