Switch bank account now and then re-mortgage next year

I currently have seven current accounts and four regular savers. The reason I have all these accounts is to benefit from interest rates. I occasionally switch between banks. I must of switched five times within the last three years.

I am thinking about opening an M&S account to benefit from the switch bonus and regular saver. However, I will be re-mortgaging next year (around March-April). Is it worth avoiding the switch because of this i.e. because I am planning to re-mortgage within the next twelve months?

My Experian credit score is just over 900.