My car is a 2010 vauhall Astra, if I try to get into first or second gear it feels like there's something physical blocking me. When I lift up the trigger on the gear stick, that you usually use to get into reverse, I can get into first and second but I can't find any way to get it into reverse. I have booked it into a garage on Friday, is it unsafe to drive until then?
I wouldn't expect there to be any safety issues, as long as you can shift safely when holding the trigger that is. Mechanically the worst case is your car stops shifting while you are on the road and you have to pull over, which is usually more a question of inconvenience.
If you get lots of grinding of gears or slipping I'd recommend you don't drive it as you could be damaging the gears and/or clutch, you're better off getting a tow.