We stayed here for 8 days and used it as home base for a variety of tours and outings. It was very easy to get to the London Underground, and just a short ride to train stations including London Bridge and Waterloo.
The apartment was in a newish building, perhaps fifteen or so years old. It had a full kitchen, including a washing machine, though the washer was challenging to use because there was no manual and the management was unable to provide accurate instructions. Notwithstanding, the kitchen was well-equipped and we cooked nearly all our meals here, or made lunches to take with us - this was how we helped keep our vacation affordable. However, it should be noted that we did feel the need to perform a very thorough cleaning of the kitchen before first use as it still had some "artifacts" from the prior tenant.
Our "flat" had two washrooms, one for the main bedroom, and another for the rest of the apartment. The managers provided a set of towels, though surprisingly would not provide any clean replacements for the duration of our stay, except at added cost. Same policy for the bed sheets. We did get bath and dish soap after asking several times.
One irritation involved the "damage deposit." Zen Apartments would not accept a credit card and insisted on cash or wire transfer. Then, at check out, the manager announced she had not received payment from Expedia and would not refund the deposit until said payment had been received. This was a hardship.