Sounds to me, and from your description, that you have two problems
You said that you had to press hard on the button to lock it and the unlock button was fine? This indicates that the actual button was failing, not the whole fob
Do the boot and headlight buttons work ok? Try both fobs
You also say that you have to put the fob in the slot for the car to see it. This is a totally separate problem.
there is a transponder in the fob, it could be the glass type or plastic, I don’t know, but this is not connected to the fob battery in any way. Some folk say it is, but it isn’t - trust me.
The car is sending a unique signal out all the time and this induces a tiny voltage in the transponder which, in turn, sends a signal which the car recognises, letting you start the car
it’s pretty unlikely that the transponders in both fobs have failed, so the problem, I think lies with the car’s receiver which is in the dash, close to the slot
in my humble opinion, I don’t thing shelling out a small fortune will fix all your problems, you can get the buttons on your fobs fixed, do a search for keyfob repairs, you can also get the switches from ebay for a few bob and do it yourself
This is the longest reply I’ve ever written!!