Having owned the car for 7 years and about 50,000 miles 1st and sometimes 2nd gear selection has always be difficult to engage at times, especially at standstill, I suspect a synchro/baulk ring issue, its had a new clutch kit and DMF 12 months ago, so had the gear oil changed at the same time. I have learned to live with the issue, the trick is to pop it into first while the car is still rolling slightly. I have heard a couple of people say it could be an adjustment issue at the cable end, Is there any method of adjusting the selector cables (apart from the neutral/fourth "reset" trick), As far as I knew there wasnt.

Secondly there used to be several posts on the net about upgrading the gear oil to that of the Focus RS. that makes a slight improvent on the shoft, but I cant seem to find them and what spec oil it was. And last but not least on the ST gearbox, mine anyway, there is a drain plug and a fill plug, but also a similar plug on top of the box, in the selector area, again from looking aorund on the net, some owners say this is the factory fill plug, so the box can be filled via this, or as I may consider adding an oil additive. Is this correct as I have my doubts.

I wouldn’t use any additives, use the recommended Castrol gear oil, just changing the oil will improve things anyway, normally a good practice to change the oil every 30k at least. Use Castrol Syntrans FE 75W, around two litres will be enough. 

good advice, thanks. It had new oil when the clutch was replaced, but I dont know what oil they used, so I may just change it any way 😉