Sumdog - perfect for all you key maths skills - https://www.sumdog.com/user/sign_in
My Mini Maths - check out the practice arithmetic papers - https://myminimaths.co.uk/year-6-mini-maths/
Khan's Academy - it is American, but if you are stuck on a particular topic in your revision guides, there are some really useful videos and practice tasks - just search for the topic! https://www.khanacademy.org/math