The vertical profile doesn't look odd to me. Looks like a regular rate of descent unless I've missed something. What is your interpretation?
It's not that easy to see on the graphic - I probably should have exaggerated the vertical scale to make it more obvious.
The Phenom is approximately 1250' AMSL when it's roughly abeam the motorway junction (top LH of picture), but by the time it's over the scrubland just S of the A30, it has climbed to 1750' (EGLK elevation: 325'). Fifteen seconds later, it's descending at 3000 fpm as it intercepts the runway heading.
The data is from an in-house ADS-B monitoring project that my company runs, mainly focussing on LHR arrivals and departures, but by default we capture data from other flights in the vicinity.
And yes, before anyone asks, the AAIB have been made aware of the existence of the data.