Hello, Raymond, and welcome to GE.
Can "for a few days" be moved to the beginning of the sentence?
For a few days, he has gone to London on business.
I don't think so. This position of the adverbial is typical of perfect tenses, the sense of which is completed by the adverbial that comes after them. For example, I don't think we'd normally say something like this in isolation:
- For a few days, it has been raining.
However, front position can be allowed by context:
A- I'm fed up with this rain.
B- It is true. For a few days, it has been raining a lot, but the good news is it will clear up soon.