EDIT: This time the numbers are correct, I think
The UK limit is 100W at the transmitter and 200W eirp.
A dipole is 0dBd gain or 2.15dBi.
100W is 20dBW.
100W into a dipole is 22.15dBW or 164W eirp.
100W to a dipole is OK for the UK.
WRC-15 rules are 15W eirp and we'll use the same dipole.
15W eirp is 11.8dbW eirp which is 9.6dBW into our dipole or 9.14W
Probably, allowing for feedline loss etc. 10W into a dipole is just, just legal for WRC-15 allocations.