Okay, so I what I am now considering is adjusting the layout plan, attached. (Current layout on the left, potential new layout on the right.) This should not require license to alter, according to the rules of the lease.
This would involve:
1. Confirming with a surveyor that the coat room walls are indeed not bearing, and removing those internal walls to increase the floorspace.
2. Leaving the toilet in the top left of the room and putting the sink in the top right, which should mean that no new pipes need to be fitted through the exterior (bearing) wall. (The sink and bath can both feed into the current bath wastewater pipe.)
If I do this, my inclination would be not to inform the freeholder, as I do not believe I would need to do so under the lease (which only says altering bearing walls needs a license); if I did tell them, the worst case is that they could dispute it or say that that if I want any form of written consent then there will still be a charge.
But, when eventually selling the property, I would then need to state in the sale docs that works had been done in the property - in this situation it would be preferable to have some form of consent from the freeholder in case the buyer's solicitor questions this. Or am I over-thinking it? If the alteration is not prohibited by the lease and I have all the appropriate construction/surveyor documentation, surely that is enough for the buyer?
Plan B.pdf