We've tried two:
Conquer Maths has an Australian chap that runs through lessons (only as a voice, no video of him, although there is a display like a white board where everything appears), then there's a series of questions to apply learning.
It also has tests for specific topic areas, both short and long tests (so you can check if a topic is secure or needs revision). It has a quick fire section for learning number bonds and times tables etc.
It goes all the way up to Year 13 (so covers reception, then KS 1-4 + years 12 and 13)! And it covers ALL maths topics, not just calculation. Certificates are provided to print out.
The down side is that although aligned to the UK curriculum it is the old one (I think), however year 6 has Roman numerals and long division, so they may have updated it. Not a huge problem because everything is quite clearly set out and accessible - you just find the lessons you want, click and go.
Maths Factor has video lessons with Carol Vorderman, it's slick and well organised, and follows a natural progression. It is quite slow and repetitive, however as a parent you can move your child to any lesson available. There are also certificates you can print out and marbles to earn. The mini games area is fantastic, with excellent games to reinforce all of the main calculation skills. There are other areas available that reinforce specific skills like times tables.
The grand genius test that DD completed, however, was a let down (DD felt disappointed) because it related only to the last module completed, rather than the whole series of modules she'd completed over time. We hopped over to Conquer Maths and she completed their test covering the same topic (fractions) and it was what she had been expecting - a test that covered all the fraction modules she'd recapped on Maths Factor.
The other main downside is the focus is very much calculation, so no time, symmetry etc.
Conquer Maths used to be much cheaper, although it now costs the same as Maths Factor, however as it seems to cover everything over the whole maths curriculum and has much better diagnostic tests, it is, imho, the better value option between the two.
HTH