A word of caution with aptitude tests. Its a bit like 11+. Some will sail through with little or no preparation. Others will pass after masses of preparation. And some will be caught out, partly though taking at face value statements that preparation is not needed. We were told that BMAT was a more predictable test than UKCAT for those from private or grammar schools with good teaching. Which suggests that those with more variable teaching might be wise to check they had covered the basics.
On low UKCAT scores I agree completely with a dispationate look at your DCs strengths and weaknesses. They dont have to be good at everything. Then spreadsheet.
Plymouth Keele and SGUL are obvious. Birmingham Cardiff and perhaps Nottingham (DD was another who got caught out) for those with good GCSEs. Perhaps KCL and Liverpool if the UKCAT is weak but not awful. It might also be worth a look at Belfast (a very high acceptance rate), Dundee and St Andrews. There seems to be lower competition for St A places with clinical in England, as Scottish students dont want to pay fees. And the cut offs for high UKCAT places often seem to yoyo, so it is worth looking back a few years. Its high one year so lots of people are put off, so the next year it is low etc. Look at the 5 new medical schools.
It is often worth looking closely at local medical schools. They really want to train students who will stay in the local area, especially if there is a doctor shortage. And perhaps especially those with an interest in rural medicine etc.
And if all else fails remortgage the house and try Buckingham. Private. Fees are about the same as a good boarding school. But you can apply after results in August and start in January and with four terms a year you finish quicker. (And Buckingham U tops this years student satisfaction tables.)
Good luck. DD was lucky that Bristol did not look at UKCAT. I am so sorry that door is closed.