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To get the best recommendations for lodging, you should provide your budget per night in GBP (not USD.) In general, it is advised to stay within the Underground (Tube) Circle Line, but it really depends on price per night. Three days is very short, I would advise no less than 4. FYI. I brought my nieces to London (after being in Scotland) for 4 days and barely scraped the surface of what there is to do in London.
What are your interests? Art? History? Walking tours? Architecture? West End shows? I've been to London 73 times and still have a long bucket list of things I want to do!
Duplicate of your other question surely.
The same is still true, we need more details to give recommendations.