For all gas safe members, when installing a condensing boiler in a bathroom/toilet, can the boiler then be covered with a wooden cupboard, and is it legal to place the boiler above the low level toilet cistern, venting through the exterior wall to outside over the footway in g/f terraced property and almost next to the front door.

Is the footpath public land or even shared land?

Boiler can be in a cupboard and over a cistern as far as I know (other than the poor ergonomics). Just check manufacturers instructions for clearance and vent requirements. The position of the flue is pretty tightly regulated but easy to work out. There’s a good diagram in part J

http://www.selfbuild-central.co.uk/regulations/building-regulations-and-standards/j-combustion-appliances-and-fuel-storage-systems/

For all gas safe members, when installing a condensing boiler in a bathroom/toilet, can the boiler then be covered with a wooden cupboard, and is it legal to place the boiler above the low level toilet cistern, venting through the exterior wall to outside over the footway in g/f terraced property

My neighbour has done exactly this bar over a cistern in their extension which has just been finished.