I finally recovered my bike from the bike shop after paying over £175 in repairs. It still isn't fully fixed - the seat is a bit wonky and I'm sure the back breaks are playing up slightly. It makes an odd and annoying noise when I stand up to set off from stopping at lights.
Back to the gym for a decent cross-training session on Saturday - a bit of resistance training and a decent 35 minutes on the cross-trainer. All good preparation for the long run tomorrow.