Welcome, you must be super excited with your new "beast"!!
Not sure if you wanted to play on the Mersey!! If so there are a number of launch sites but by far the best and most economical is Liverpool Sailing Club. I had a guided tour last week and for an annual membership (not too expensive) you can launch 24/7/365. Every member is given a set of keys!!
Great bunch of guys too. Check them out - Liverpool SC
The alternative is to launch off New Brighton (Need a permit from Wirral Council) or pay lock out/in fees (£11 each way) at Liverpool Marina!!