I'm an Australian with a UK registered bike. I crossed from Bosnia to Montenegro at Scepan Polje (SE from Sarajevo via Brod) in Oct just gone, and all there is no cost/hassle for you and if you don’t have a green card you can buy one at the border for 10euro.
For me I only just bought that bike 1 week before leaving London and the dealer had used ‘white-out’ on the registered owner names and then re-written my name/details so it was kinda funny when the border guy looked at it, figure it was stolen, and said “no Montenegro”. Also it was 9pm and the potholed or sometimes dirt road i just came down from Brod sucked on a Ducati ST2 so I was not keen on going back that way! But I convinced their boss I owned it eventually.
Also, when I entered Serbia from Bulgaria near Zajecar 1 ½ years ago on an Australian registered bike I didn’t need insurance or pay anything.
For Albania formalities I just posted a response on the link that Pietro just added.
All of Montenegro is excellent, especially SW of Podgorica. Detour via Rijeka if you ride around that way – it’s hardly been developed and very picturesque. Hotels are usually around 15euro though in Niksic there is only 2 hotels and cheapest was 23, but it was fun on a friday night (and home of main brewery). I didn’t see any camping places so if you wanted to save $ then I’d consider it safer to rough camp when you’re in the mountains. If you are 2 lads I’ll add that there is some very nice and friendly girls throughout, but they ain’t as easy as I thought! I’d be interested to know if you have any luck on that front. Forget girls in Albania.
In Albania you can usually find or hassle the hotel owner down to 10 euro and I chose the hotel based on where I could lock my bike before seeing the room. When the only other large bikes all have foreign number plates you don’t feel so comfortable considering their reputation for theft. Plus the citizens on average are well armed so if they did ask for your bike you better have a nice smile, but that is not really likely, I’m just winding you up. One local guy there with a bike shop reckons possible theft of your bike within the country is extremely unlikely as while you’re on it they’d get in too much trouble, and not while it’s parked – even in a hotel, cause they’ll assume that it is owned by a fellow Albanian.
I stayed on the main Nth-Sth road because I was on an ST2 but my Greek mate (lives in Bulgaria) rode along the coast where more roads are gravel and he concurs that Girokaster is probably the most interesting place. Pietro seems to have the rest of the places to visit covered.
Also, when I was stopped by the police for speeding (possibly 140 in an 80-Mallakaster range was fun!) I spoke lots of English words quickly but without making sense and so he let me go. Enjoy the diplomatic immunity!