Quick update - 1st 2nd gear selector arrived today (NOS) still wrapped in brown paper. Big difference in wear (see pic) all back together and feels remarkably better. Road test tomorrow .
Lack of lube?
An old pal of mine had a cortina Mk3 used to jump out of 4th , he sorted it with a bungee cord tied to lever and seat ( he wasn’t a real mechanic)
No bungee cord found . All the gears and selectors all seem in really good nick it was just the jumping out of 1st and sometimes 2nd on the overun. Lived with it for nearly 2 years and this month was to do the jobs i couldn't be bothered with. Today was road test day and it was a complete success. Just need to get confidence back in pulling away in 1st so it doesn't make me sh*te my pants with a massive 'bang' when it used to pop out of 1st.