Lake District offers excellent kayaking opportunities for beginner kayakers. Keswick is a good place to start as you can rent kayaking gear from the Keswick Lakeside shop. You are faced with flat and peaceful waters and an absolute beginner will find it a tranquil experience. The entire area offers plenty of parking, restaurants, accommodation and very well developed.
Another great place for beginners is in Devon at the Salcombe-Kingsbury Estuary where you can enjoy wildlife like wild fowls and other bird species while on a peaceful practice paddle. It might sound like a boring expedition, but while enjoying your outing you will see plenty of hidden creeks and coves that you would have missed if you did not decide to try water sports. Even though Salcombe-Kingsbury is tidal, you will be perfectly fine to set off when it is mid-tide as you do not want to miss out on any hidden gems.
When you are new to kayaking and learning, two other gems that will be great to test the waters are the South and North Sands. All these waterways are mainly frequented by beginner kayakers and you will always find a tour guide and kayaking guides in any of these waterways.