My 15 plate Fiesta 1.0 Zetec S Red Edition has recently (past month or 2) developed a problem with the oil tank overfilling and being diluted with fuel. The local garage recommended to take this to Ford for diagnostic as they weren’t able to do it. The oil will need draining and replaced roughly every 3-4 weeks if I let it continue due to the leak. 
 

I've taken it to a Ford garage today and essentially wasted £95 for them to tell me they cannot work on it due to several suspected reasons, it’s got a cold air intake (I installed this about 3 years ago), they suspect there is no catalytic converter (this has not been removed and shocked this was suggested) and suspected the engine had been mapped (it’s not been mapped). I explained the latter 2 were not correct and they refused to do any work to help me solve the issue and recommended I go to a mapping specialist? I find this so frustrating since this issue has only started recently and nothing has been changed on the car.

 

I’ve seen a few forms regarding similar issues but I am not sure what to tackle first, which will be the cheapest. I feel like the issue started around about getting it serviced, but this may be coincident. I did have a fault a while back regarding idle bank 1 being too rich, but this never came back after being cleared. It also had the O2 sensor replaced near the cat within the last 12 months due to heavy fuel ratio which then passed emissions. 
 

I can put the factory air filter back in as a first step and will try new fuel injectors but has anyone had this problem recently / know of the most common faults?

The High Pressure Fuel Pump may be leaking Petrol back into the Engine.

Update:

I’ve replaced the high pressure fuel pump, cleaned and check gap of spark plugs and cleaned / serviced the fuel injectors, which were very clogged. 
 

It was also recommended by a garage that the high pressure fuel pump was the issue, but fuel is still getting into the oil and the car is running very badly now, regular stuttering at lower rpm (below 2000) and feels like less power. 
 

I’ve got it booked in with a different Ford at the end of October, after explaining my previous issues, but do not want it to carry on that long and cause an expensive bill at the end. 
 

There is a strong smell of unburnt fuel that can be smelled while driving and the engine is running hotter than usual. There are no visual leaks under the car or over the engine, but it’s losing fuel way too quickly, any other recommendations?