My MK2.5 is in pretty solid condition and I'd like to keep it that way. Are there any specific areas I should be checking and rustproofing to keep the bodywork in good condition?

The Mk2.5 doesn't really rust like the older Focus' did.  If you see a rusty one it's usually had a poor repair in the past.  You could remove the plastic sill trims and have a look above them for peace of mind.

Rear arches at the front of the wheels both sides, inner rear arches inside the plastic liner will rot from the inside out then form bubbling on the outside mostly on passenger side. Also pay attention to the under edges of the tailgate trim at each end will flake and if you are lucky the passenger rear door where the water drains out. Best to remove the rear arch liners and clean up as much as possible and if rusty get some direct to rust hammerite if not rusty then some hammerite under body seal with added waxoyl. The rust on the arch in front of the rear wheels travels forward to where the rear panel joins and flakes just behind the passenger door which you find when trying to sort out the rust. I removed all the rust and then used some rust convertor then painted on some high build primer over days building it up.

1 hour ago, F0CUE said:

Rear arches at the front of the wheels both sides, inner rear arches inside the plastic liner will rot from the inside out then form bubbling on the outside mostly on passenger side. Also pay attention to the under edges of the tailgate trim at each end will flake and if you are lucky the passenger rear door where the water drains out. Best to remove the rear arch liners and clean up as much as possible and if rusty get some direct to rust hammerite if not rusty then some hammerite under body seal with added waxoyl. The rust on the arch in front of the rear wheels travels forward to where the rear panel joins and flakes just behind the passenger door which you find when trying to sort out the rust. I removed all the rust and then used some rust convertor then painted on some high build primer over days building it up.

Do you park in the ocean?   I'm honestly yet to see a rotten Mk2.5! 😮 

@tomfocus I'm near the sea in sunny Scotland lol

On 4/10/2019 at 12:38 PM, F0CUE said:

@tomfocus I'm near the sea in sunny Scotland lol

By "sunny" I assume you mean occasionally see the sun? 😀

4 hours ago, 1979Damian said:

By "sunny" I assume you mean occasionally see the sun? 😀

Yep exactly lol