Found a guide here for helicoiling a subframe bolt and ordered a kit .
new cat and o2 sensor where fitted by a garage in 2017 and 20,000 miles ago according to the history. Cat was £100 and sensor was £80 so probably not the best.
I have a cheap scanner basic scanner that gives the p0170 fuel trim bank 1 fault but nothing else.
Did a freeze frame reaading for when the mil light came on and got :-