Originally Posted by Ldnn1

I would clarify this slightly - the change from the Elizabeth Line to the Thameslink southbound at Farringdon is actually incredibly easy and has pretty much zero walking if you sit in the rear carriage of the Elizabeth Line train. The lift is right behind the end of the platform and takes you straight up to the southbound Thameslink platform to Gatwick (don't go all the way up to ground level). So even with luggage it's pretty easy, albeit you may have to wait a couple of mins for the lift.

For completeness - in the reverse direction LGW-LHR, there is no lift direct from Thameslink north to EL - you have to go either down one escalator (still very easy if luggage not too big) or up in a lift, across the concourse and down again in another lift (the one I'm referring to above).

Of couse there is also some walking / lifts at the LHR and LGW ends between platforms and terminal but I don't think that's more than from the coach stops.