I have the same challenge. Bunny lounge gets slated on here for value and service. Jason also posted about what was in actual fact a walk in in Euston that I visited without recognising It. He changed his rating to not recommended after subsequent bad experiences. Also read his review of the chica's in chalk.farm?
Best I can recommend is to build a long hotlist specified by geography (I use Local, Central, Outskirts, Other), take an interest in the actual (as opposed to advertised) hours your favourites work,and keep an open mind when arranging a punt. Having some reliable, not popular "back ups" is increasing my hit rate. I have also started preferring my local vacinity although this has its own limitations. Living in one of the right areas in London will help but not that easy to fix.