Dagenham is a dump. It's the sort of place where Poundstretcher is regarded as an upmarket store. I've found some perfectly acceptable 'working man's caffs' around there but don't expect to find many (if any) smart restaurants or any decent shopping.
Much of the borough of Tower Hamlets falls into a similar category but the area around Tower Hill is its saving grace. The area is primarily business orientated; you won't find many shops in the immediate area. The obvious major tourist attraction is, of course, the Tower of London:
http://www.hrp.org.uk/toweroflondon/
(Expensive but worth a visit if you don't know London).
There are quite a few decent (if somewhat pricey) pubs and restaurants in the area.
However, the best thing about staying around Tower Hill is the ease of access to all of central London's sights and attractions. Tower Hill underground station is on both the Circle and District Lines. Take a westbound train to Embankment to get right to the heart of things. (The trains runs every couple of minutes or so. The journey takes around 10 minutes). From there it's only a few minutes walk to Trafalgar Square, the National Gallery and Covent Garden. I particularly mention Covent Garden because it's packed with great restaurants and bars and there's always plenty going on.
If you're into museums, stay on the westbound tube train for another 10 minutes, to South Kensington. The V&A is unmissable (check out the fashion collections), the Science Museum is great for 'grown-up kids' and the Natural History Museum is just stunning.
Those are just a few suggestions. If you're staying around Tower Hill, all of central London's attractions are within easy reach.
Chris