The reliable way to hire a tradesperson

Super amateur painter, I’m creating panelling in my room by using a 9mm sheet of mdf and routing grooves in them to create a ship lap effect and sticking this to the wall. Will I need to seal/ prime the mdf and what paint will be best as the top coat for this? It needs to be quite durable as it’s for a kids play room TIA

I am confused? I have had 4 quotes for a new combi boiler. Two of the quotes say I new a pipe upgrade and Two say I don't? My boiler is in an off shot galley kitchen (next to a normal gas cooker). The floor distance from the meter (in the cellar) is approx 10/ 11mts. There are a couple of bends that take the pipe from the cellar to the kitchen. The pipe is 22mm all the way. I have looked at a 24kw Ideal basic Boiler and a 30kw Ideal Logic Max. Which company should I believe?

My daughter lives in a terraced house fronted with engineered brick. The whole frontage needs repointing and several tradesmen have said it should be pointed with lime mortar. Since the bricks are non-porous and don’t breath, why does the pointing need to be lime and breath? Surely the pointing mortar should have similar properties to the brickwork.?