Is this sentence grammatically correct?

There is no reason to use a continuouss tense. Just say I was on holiday in London this summer.

And only being on holiday allowed me to work in London <<<< I don't understand your meaning,

actually i have read this sentence in a website where they have asked to join the two sentences using conjunction ' but for '. i knew that we can just write I was on holiday but i want to know whether we can use "was being" as well

"I was on holiday .... but only being on holiday allowed me to work ... " The correct conjunction would be "but" because of the implied contrast between holiday and work: e.g. "I was actually supposed to be on holiday, but only because I was there on holiday I was able to do some work."

The use of English around the world has many variations but understandably we are aware of its origins as being England. So why do Americans have so many words to describe things that already had words in British English

I say thank you much, even though it's informal, because it is informal. The informality is intended so as to not seem pompous or condescending in my thanks.

I don''t think I've eve heard anyone say 'Thank you much'.

AnonymousI was being on holiday in London

No. You can't do that. To be being is used for temporary attitudes, often negative.

I was being ornery, so I didn't comply with their requests.
Lucy was being uncooperative with the school principal.
Steve was being a jerk at the bar last night.
Wilma was being a real flirt with Joe.

thankyou it helps me a lot