I am filling up my tank fully and I am only getting approx 100 miles out of it. I know this isn't right. But I don't know how to get it sorted without costing me lots of money. 

You must have a leak somewhere that or something is seriously wrong, I think @iantt will know I lot more on this issue.

Even my 2 litre Focus doesn't drop below 3/4 in 100 miles, so as Ryan has said you have a serious issue there!  It has to be a physical leak, as there is no way a 1.2 can burn that amount of fuel.

First place I'd look is the fuel filter.  Especially if it's an "OEM Spec" replacement part!!

They look fine with the engine off, but as soon as you get flow through it, the fuel just pi...wee's out

Sounds pretty good to me [emoji618]️ well it is for mine

Seriously I'd start it up and get underneath see if you can see fuel leaking out when the accelerator is pressed

On 01/03/2017 at 4:31 PM, Philf1 said:

Sounds pretty good to me ️ well it is for mine

Seriously I'd start it up and get underneath see if you can see fuel leaking out when the accelerator is pressed

How many miles do you get out of a tank on that beast?

Anywhere between 20 and 26 mpg but small tank so filling up twice a week. I never let it get too low 1/4 at worst so costs about £35-£40 a time

I'm jumping in a bit late but I had this type of problem a few years ago with the Vauxhall Omega I had. It was due a service so took it to my friendly 'engine dweller' who quickly found that I was continuously running in what he called 'get you home in an emergency' mode. I never noticed! I still got 70 out of it, yes, it probably was a little sluggish., but nothing I really noticed and thought 'I'd better get this seen to' until I started noticing the fuel consumption was getting worse and worse. ( much better than 100 per tank......how is the tank? :-)