My son seemed to do well with the Schofield and Sims books.
No fancy gimmicks like colour or stars - and pretty preasonable prices. He really preferred these over the expensive ones from WH Smith and so did I. They were great for KS1 and especially the KS2 series - I wish they did a KS3 series but sadly they don't.
AE tuition also do a good mutiplication workbook set good for 7 year olds.
we use the S&S KS2 mental arithmetic ones with our 7 yr old. Could you let me know which are the KS1 ones, as we have a 5 yr old who likes maths too.