Can anyone recommend a cheapish but good aparthotel in London please?

[goingtobefree]

I have family visiting from the other side of the world to visit us/London.
They are close family and this is possibly the only time they could afford to visit this country.
Me or my DH will take them to London to mainly sight see beginning of June.
Can some one recommend a decent place to stay-a family of 4 with two teenagers plus one of us.
We are planning to stay for 2-3 days max.
Obviously we would be paying for hem to stay, visit etc., but would like to keep the cot down as much as possible, but at the same time don't want to stay in some dodgy place.