Hiya matey. Is the circlip in place on the gear lever, it's the one
that goes down on the big rubber bush/gaiter on the base of the
gearstick??
My 1600E used to do exactly the same thing, go into reverse instead of
first, my clip gad broke. If you remove the soft gaiter/cover on the
gear stick there should be a big rubber doughnut looking thing
underneath. There should be a circlip round the gear stick pushing
down hard on the rubber, it's this rubber doughnut that acts like a
spring and keeps the selector hard up against the "gate".
There should be a diagram/picture in the workshop
books............................ that's about all I can think of
apart from a very expensive alternative.
Best of luck
Gary (from Dagenham, home of Ford)