Arresting the rust

[Spailpin Fanach]

I bought a 1989 Westy a few weeks ago and very happy with it. I use it regularly, especially weekends, and keep it in an underground garage. It was kept in the open for the first few week. I've noticed rust patches forming recently, pics attached.

What action should I take to stop/inhibit/slow down the spread of the dreaded rust. The rest of the body seems to be in good condition and was well looked after by the previous owner. 

I intend to keep for several years and would like to restore to as perfect a condition as possible. 

[TONYT25T25]

All the favourite places, the windscreen rust is common and normally needs removing to repair properly as the damage is not visible until you do this, I patched mine up when mine cracked but normally needs a welded patch (check inside under the mats for any water ingress).  The seams are a similar problem and sometimes you can grind out a bit and patch.  The bit near the jacking point near the trailing arm is also a favourite spot and could be an MOT issue.  I gouged the area around mine and treated with rust inhibitor but I may have been lucky as the rust had not penetrated to far, this area needs to be inspected from all angles due to the importance of its use.