This is one of those problems I sympathise with you over . as my step son has just bought a 51 plate fiesta 1.25 and it had several issues that we have had to work through with the same moaning about cost and time .
You seem to have worked through several things that are logically correct , but you mention several things of interest , one if you move slightly it goes back to idle , no fault codes present , iscv replaced and now seems worse and tps replaced twice .
No DTCs would suggest no faulty sensors , as in failed , but one is possibly giving an unexpected result
The fact that it improved after replacing tps and resetting ecu but as soon as it had read the sensor map it went back to the same would suggest it is trying to prevent stall or something else
The fact that you say that if you move car it then drops but then I assume as soon as it comes back to standstill , it does the high idle again might suggest vehicle speed sensor but seems a bit far away from core issue to look at .
If I was you I would try and understand where the idle speed is being fed from , you have replaced iscv , I would try removing it from manifold and block the 2 holes and see if it idles low or at all , or is still idling high to remove that as a possible cause , then I would check the throttle is fully closed during the high idle , it may well illuminate the engine light as you will loose the maf flow but if plate is shut and iscv removed it has to be a vacuum leak in the manifold or gasket and the situation is as soon as you move the vacuum leak is "overpowered" by the required air so until the vacuum is built up again and the threshold of gasket or crack is reached it is ok again .
If you think it is a vacuum leak in the manifold and all pipes seem ok then carefully at idle spray some brake cleaner CAREFULLY and lightly in small areas around the manifold , if it gets sucked in and the idle speed fluctuates and the resultant smell from the exhaust would trace it .
It is always difficult to diagnose this type of fault , just stand back and think "where is it getting the air " then look around carefully .
Hope my babbling helps in some small way .
