Great work!
The most important thing is for it to feel 'normal' as you lose the weight. There is nothing worse than feeling like you've given up the earth for no good reason.
If you ever need to keep your motivation, go to the weights section of the gym and carry around a 5/10kg dumbell/weight for a bit and see how it makes you feel (i.e. see what you were carrying around pre-routine).
Regarding your hip, how is your flexibility on that leg? Can you lie flat on your back and get your legs vertical whilst keeping them straight? If you squat without a load, how low can you go before it starts hurting?
Before getting the MRI, it may well be worth getting a GP to refer you to a physio, or even stumping up the £50 for a physio consultation. Reason I suggest that is I have a lower back problem that a physio spotted (and resolved), whilst the GP referred me for x-rays, blood tests, etc. and just gave me painkillers to "deal with it." See a physio, determine if it's a muscular/soft tissue problem and go from there.
Doctors are great with things that are broken and obvious, but GPs are genuinely useless (unless you get either a good one with an interest) with soft tissue (unless they're fixing it, or do orthopaedics).