Hi, I am a novice DIYer so apologies if I don't make perfect sense. I live on the first floor of a 4 story Georgian apartment building in London (on top of the ground floor apartment) and am wanting to replace the bath with a walk in shower. I would like the shower tray to sit as flush to the ground as possible, which will mean dropping the pipes down approx 12 - 13cm from the current level. In addition to the internal work, this will also require creating a new hole in the wall for the external output pipe. My query is around dropping the level of of the external hole as this will have a direct affect on the roofing of a glass conservatory type structure belonging to the ground neighbour. I have attached photos of the glass roof and the current position of the external output port for the shower. The glass roof is sealed with a strip of lead and dropping the level of the pipe by anything up to 13cm would mean: 1. cutting into the lead 2. lowering the bottom level of the pipe to approx 5cm above the glass line from the current level of approx 18cm Before I discuss and agree anything with the neighbour, I'd like to know first if this all sounds physically possible and within UK building regulations. Any advice much appreciated!