The following websites offer little mini arithmetic papers to support pupils' mental maths knowledge.
Again BBC bitesize is always a good starting point for revision.
We also see that it is essential that pupils see the relevance of Maths. This website provides some great practical activities that you and your child can complete together, which will support your child to develop a concrete understand of the maths concepts applied.
Finally, NRICH provides some great maths challenges to encourage your child to think critically and logically when approaching mathematical problems.