German translations for the following phrase...

Dont care if its slang etc, but i need a one liner which basically sums up "I am more than disappointed and a bit pissed off"

Nothing majorly crude, but something to put the message across I am not a happy bunny.

Thanks.

"Ich bin sauer" perhaps?

possibly, but its signing off something, i wouldnt mind for example "thoroughly pissed off, Schotte"

so instead of a "yours" or "best regards"

get me?

stocksauer ...

lol i like it but thinking it might be slightly petty in this current situation im in

is that received quite rude?

im talking to a big company here so i dont want to be a prat but they have messed me about.

How about "maßlos enttäuscht und verärgert"?

how might one say "this is not the germany that i understand" ?

Dies ist nicht (das) Deutschland wie ich es kenne ...

including the bit in brackets?

your choice ...

incl. "das" without the brackets (das Deutschland) - or without "das" and brackets altogether (Deutschland)

Leck mich doch am Arsche, was soll die Scheisse? Trust me on this!

ok im not wanting to totally burn my bridges lol... but cheers

"ich bin schwer enttäuscht und stink sauer"

How's that for you?

"Ich bin mehr als enttäuscht und ziemlich verärgert" - that's about as literal and polite as it gets.

As for the salutation I always find "Hochachtungsvoll" after an irate letter pretty effective. But

"In Erwartung Ihrer Erwiderung verbleibe ich
Schotte"

has a certain appeal. No salutation at all.

How about: So kenne ich Deutschland eigentlich nicht? Depends on the context of course.

As for signing a letter off, the "hochachtungsvoll" is very formal but out of fashion, hence it's cool if you're pissed off. To add an insult you could write:
"Mit der Ihnen gebuehrenden Hochachtung" which loosely translates as giving you the respect that is due to you. But coming from a foreigner the recipient may just shrug it off not expecting you to know these finer points of sarcasm...