A garage side door that doesn't swell

[Sprogginz]

I have a garage side door that now expands so much during the crappy months that I have to gain access to the garage via the main up-and-over door, then kick the side door from the inside to open it. To close it, I have kick then it in from the outside!

I believe that if I trim the door, then during the summer it will shrink so much that the latch might not catch properly and not lock.

Can this be fixed?
Once it's shrunk, is there any magic formula that I can paint on to stop it swelling again?
Maybe I used the wrong wood to make the door: I used pressure treated external wood to make the frame and marine hardwood plywood for the cover.

If there is no way of stopping this with my existing door?
Are there alternatives? I've looked uPVC doors but they're more than £300.
It seems most ready-made doors can only be trimmed by a couple of centimetres but I need to trim one right down to just 183cm.
Maybe a metal door? That doesn't expand but I'm sure it'll be big bucks too...heavy sigh.

Thanks very much and hope you can help.

 

[foxhole]

Plenty of second hand Uvpc doors cheap or free on Facebook markets place .

 

[Sprogginz]

Thanks, unfortunately none of them will be just 183cm in height.

 

[freddiemercurystwin]

I have a Latham steel door on my garage, it's absolutely excellent but sounds like it'd be over your budget.