Do I PVA concrete floor

Not pva this forms a skin which could be peeled off, you should use SBR on the concrete, put it on with a mini roller with tight spong, you then lay your thermal boards on thin coat of rapid set flexible tile adhesive (fine notched trowel) let this go off as the boards will slide about when walking on them, then lay your warm up cable onto boards (no pva!) I then pour self leveler over entire area, do this at the end of the day so you can walk away from it to dry, it is good practice to self level as it protects the heating Cable if you ever have to take a tile up, then tile on top as normal. The electrician needs to come prior to you starting as he will need to put in 2 back boxes, one down low for fused spur and one up high for thermostat , as you start laying heating cable the flex needs to go up to the thermostat and a probe from stat to the floor. Hope this helps

Do not use PVA use SBR, and make sure the UFH mat is working before you tile, do not switch UFH on for 2 weeks and then increase temp slowly.