why would anybody now want to formally invade the U.K
That to me is a niaive comment (unless I missed the irony). There are plenty of countries with nutters wanting to expand their borders globally. Let's scrap the military and find out, shall we? Let's not...
Here is a list of likely/slightly less likely things that would happen if we got rid of our military (in no particular order):
1. Argentina takes the Falklands.
2. Turkey takes the UK sovereign base areas in Cyprus.
3. Spain takes Gibraltar.
4. Sinn Fein/IRA take Ulster.
5. North Korea/China/Iran/Uganda or some other lot fancy the UK's wealth and mineral assets plus a seat at the EU table and invade.
No Bucks = No Buck Rogers to keep them away!
LJ