Unless it's locked, it should fairly easy to get into the glovebox. Just bear in mind that there are at least two latches. Find a YouTube video of how to remove it and you will be able to see how the mechanism works and where to put those credit cards.

As to opening the box, I had a look at our cars (Golf and Swift) to see how easy it would be to slip the catches on the glove box. I have to say it would be tricky because the catches have their sloping side of the latch bolt facing into recesses in the box so you can’t just run a credit card or something against them to depress. You need to hook back onto them in some way. I guess they all work in a similar fashion.

They’re not a common car but if you can get a look at someone else’s you can see where the catches are and whether you could then fashion a bit of coat hanger to open yours. Having said that you could spend ages and scratch the plastics badly. It’s perhaps one of those jobs where a decent indie would probably slip the catches in seconds for a few quid. As above they will have the right trim tools to get around a simple but awkward latch.