Depends. What exam board are you taking? Buy that textbook, because that'll contain the correct information from thate axm board's specification; what you will be tested on. Also, what subject is it? For maths at least, I know that AQA and Edexcel's content is practically indistinguishable. It's just the examinations' style that is different.
Maths, Chemistry, Biology and Physics are Edexcel the rest AQA
So I guess Maths I could use what I have but not for triple science subjects?
Yeah I think so. In terms of sciences, I'm pretty sure that the exam board's content is pretty different, so you should definitely buy the Edexcel workbook.
Maths, Chemistry, Biology and Physics are Edexcel the rest AQA
So I guess Maths I could use what I have but not for triple science subjects?
Yea for triple science there's a lot of content, so buy the edexcel one so you don't start learning content that's not included in the spec or not learn content you need to know as part of the spec.