Good news!
The MPG will probably 'settle'.
I assume the battery was disconnected for the work, which, I think, forgets your driving style, average mpg etc, and then 're-learns' it...?
And ... a Ford Fiesta XR2 - liked it a lot... until the head gasket went.
And ... a Ford Mondeo Ghia - liked it a lot... until the front bumper detached.
I noticed on my display that the AC option was flashing on and off today.
I pressed it once (OFF), pressed it again (ON) and it stayed on.
Will need to keep an eye on it...
( I should check the small green window too. )
Out of interest, how do you know it needs these things?
Have you been told, does it give room for negotiation, could there be other expenses, have you looked at the MOT history etc?