Seen it now!
I was on my summer holiday when the original post was made
The tyre mounted dish is my 19E dish and has lived on a tyre for about 5 years, although its in a pretty sheltered location. Even so it does blow over occasionally - I saw it do a complete forward flip once! There are a couple of wooden laths jammed up against the back of it to keep it upright.
DONT even think about putting it on top of a garage on a tyre - it WILL blow off and either do some serious damage, or hurt someone - and you DONT want an insurance claim from someone who has been hit in the face by a loose dish.
If the garage roof is the only location for it get a proper patio mount and weight it down with slabs, sandbags, buckets of concrete etc.
All my cables currently run under the window frames - we had new windows put in a few months ago so I took the opportunity to run plenty of extra coax cables under the window frame before the guys sealed everything up! (The builders though I was mad with all the coax cables!)
The flat coax window frame connectors will work fine though. Maplins sell them for a couple of pounds each.