It depends on the extent of the blockage. You might want to try pouring over hot water on your drains to flush out any soap suds and other soft debris that could be causing a minor clog. If you’re lucky, your drains might start to work properly again. No matter what you do, don’t ever use chemical drain cleaners, as they can be harsh and damaging to your piping system.
If it doesn’t work after several tries, consider calling a professional. I highly recommend LondonDrainsDirect.com for blocked drains in London. They have skilled personnel and first-rate equipment to detect every drain problem that’s been bugging your home. Chances are they’ll even be able to diagnose existing issues that might not have presented any problems yet, and that could be missed. I think getting your whole drainage system checked from time to time could save you a lot of money in the long run.