Having worked in the construction industry since 1997 it was only during in 2020 with the world going into lock down that I first realised that I could step up and deliver what my bosses at the time were doing, realising I had the added advantage of decades of resource building and a much more hands on involvement.
There was no contest, I realised I can offer real solutions at real value for money, and since then, many tradespeople I've worked with over the years have joined our little collective, enabling us to provide a whole project solution for even the most demanding designs and requirements
There's a couple of things you might check first, one could be that the lid is held down by a flush push button, these can often need to be unscrewed in order to remove the lid, additionally it is possible that someone may have used a sealant behind the lid.
i'd first eliminate the push button possibility, and then investigate whether a sealant has been used.
the outside possibility is that the lid has been tiled around, which is a bit of a bodge..and if its been bodged to the point the lid is fully stuck, you may need to remove a tile.
to be fair without examining it myself, i couldn't give you an accurate answer, but hopefully these points may help!
I personally would remove the old tiles and use the tiles you like throughout
It sounds like the flow of water on the bath is to great for the boiler.
try running the tap slower, about half of fully open and see if this remedies the issue