Correction - they are 1 double with a sofa bed - we have stayed there with our kids a few times. There's a pool there too, but I think there is a charge to use it now.
I just checked and they have rooms available at the end of the month for £108 per night or £118 with breakfast. As far as I remember kids eat breakfast free there, so for an extra £10 the entire family can load up on breakfast - worth doing it given the amount of energy needed to go around London.
Last time we went to London we stayed in a 'Hotel' nearby on Gower Street - this was an old house turned guest house rather than a hotel - big mistake. The room was tiny and totally unsuitable for use with kids. We ended up with major cabin fever. We saved something like £15 a night, but it really wasn't worth it.
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