It looks like you have part of the bowl of a clay pipe. Probably nineteenth century if I had to guess (based on what I can see of the size and shape of the bowl):
The Museum of London offers an "Object Identification" service for objects found in London.
You can also join the Facebook group River Thames Mudlarking Finds. If you post a picture of your finds there, people will often be wore than willing to help.
One word of caution if you are planning to visit the Thames foreshore in future though. The Port of London Authority have brought in a new licencing scheme. Basically you need a permit even if you are just looking at surface finds - and the permits aren't cheap!
An alternative is to join the Thames Discovery Programme and take advantage of their free (at the time of writing) training opportunities. You can then join them and carry out archaeological work on the foreshore under their licence. (Most of the time you can keep what you find - surface finds on the foreshore are unstratified and so provide little additional information. However, there are exceptions - especially if the find is designated as being one of National Importance!).
If you are in the UK, but not in London, similar opportunities are available nationwide through the new CITiZAN (Coastal and Intertidal Zone Archaeological Network) Programme.