Shale gas is hugely polluting due to the high methane release during the lifetime of a well. Puts it on par with coal! I wouldn’t worry about water contamination or earthquakes. It won’t happen in this country (to any large degree) because we are far more sensible than the Americans and we actually enforce policies.
The important bit for the UK is that it gives us more energy security. Energy security is the main game globally now. Americas gas boom has made them more sensible (for now) and stopping any new conflicts arising. Same applies for the UK. If we can be energy secure with our own resources then we can stop backing other countries and conflicts to gain more energy. It’s all politics!
I’m just writing my MSc dissertation on the subject. Really interesting topics. 14,000 words to go.