chnage the word "oh" in the following sentence and still keeping meaning same,
Oh!, i have been in a UK.
You can simply leave it out, but the sentence won't make sense. What is "a UK"? And don't forget to capitalize "I" since you're referring to yourself.
Other exclamations might be - WOW!, Egad!, Gracious!, Heavens!
The British use Blimey and I believe the Aussies use Crikey.
There are bunches of others that are in American slang.
To change the word "oh" in the sentence while keeping the same meaning, you can use phrases like "Wow!," "Oh dear!," or "Ah!." Here are a few examples:
1. Wow!, I have been in the UK.
2. Oh dear!, I have been in the UK.
3. Ah!, I have been in the UK.
By replacing "oh" with these alternative expressions, you maintain the overall tone and meaning of surprise or realization conveyed in the original sentence.