History:
Brickwork - Pointing, Restoration, Cleaning, Mossing
Plumbing - Leaky Taps, New pipes, Outdoor taps, Radiators
Loft Insulation - PIR Rafter Insulation and Rock Wool Laying
Tree Felling - Taking Down and Removing Debris
Electrical - Fixing Faults, extra Sockets, Security and Lighting
Tip Runs - Collecting, Clearing Garden Waste and Other Household Waste
Coving - Ceiling Cornices, Wall Architraves & Skirting
Garden - Weeding, Hedging, Maintenance
Fencing - Staining, New Panels, Repairing,
Plastering - Patchwork, Dry Lining, Finishing & Skimming
Answers:
Hi i think given the job at hand can be a tricky one, he should have been able to blend it all together. there is a way and a technique to achieve this. however it has dried. you cant really sand plaster (sanding will just not take enough off). the best thing you can do is buy a tool called a "surform plane". this will allow you to take off small layers at a time until you are satisfied. although the area will not be smooth anymore. then you'll have to smooth it all off with a sanding pad. i think a bit of elbow grease and determination and you should sort it!
Yes you can use natural hydraulic lime below the damp proof course. this is done often on more gentrified projects because there is so many reasons to use lime mortar over portland cement, from health reasons to structural and longevity.
Most plumbers with good experience under their belt should be able to do this. there isn't that much difference between this and a regular bath. just find a decent one with a good reputation and you should be alright.