You are a foreigner with heavy accent living in the UK. If you want to be polite getting off public transport, you can say a number and a letter to the driver. Which number and which letter?
In a very similar vein to WAF’s answer, you can also say
3Q, assuming you are not just any foreigner, but specifically a Chinese or Japanese foreigner.
This is in fact a very common way of writing ‘thank you’ in textspeak in both languages. The number three is 三 sān in Mandarin (and san in Japanese, which borrowed it from Chinese), and the name of the letter Q is borrowed from and pronounced as in English. Chinese and Japanese both lack interdental sounds, so /θ/ usually gets substituted for /s/, and syllables can only end in one consonant (a nasal). Put together, thank you ends up sounding like san kyu when pronounced by most Chinese or Japanese speakers.
If you speak Belorussian, Russian or Ukrainian and notice the driver is about to miss your stop, you may end up yelling
100P! /sto p/
Not very polite but straight to the point.
If you speak Japanese and thought the bus ride was the best thing ever, you'll probably throw up the horns and shout
If you are French, you may choose not to go to either of these extremes and settle on
5U /sɛ̃k ju:/