At £20 for the kit it’s also worth thinking of getting Smartwater but just make sure that if you use it you put the stickers somewhere prominent so the would be thieves know it’s marked.
If it’s chained both ends to something solid like a ground anchor or lamp post, covered and alarmed then you have done as much as you can. It’s a shame you can’t get a shed/garage as that just keeps it out of sight.
As others have said, if they really want it they will take it, it’s just a question of making it too much trouble.
PS. I don’t think you could install a ground anchor in the street, the council would not be too happy with that
should get me one of those…
if that went off at 4am round my way there would be trojan units there im minutes!! wicked! or maybe not…lol
how easy is it to fit ground anchors???
Depends how powerful your drill is and how solid/how much agregate was use in the concrete mix.
Can be an easy job or like mine you may need to go to the local tool hire shop and get a bloomin big drill and a load of drill bits.
Im liking wasps idea of removing the seat to look like its knackered 
plus chains etc, wonder if any military surplus stores got buckshee tripwires n claymores ? 
Use the “search” facility - there was a thread in Praise or Shame a few months ago (praise) about a guy who comes out and fits them for you