I guess from your question that you have no experience with boats or boating. Where in the country do you live, how far can you travel to look at boats? What kind of boat do you have in mind, narrowboat, widebeam or maybe cruiser? While we are all subject tl this lockdown because of the virus you would be well advised to look online at boat sales. You can find lots of sellers, from single boats to hundreds offered on the same site. All or most brokers will have online sites and from there you can soon see boats that you like the look of.
Some years ago while looking for our boat we visited one large broker in the Midlands that has been mentioned in answers above. We told the guy in receptione what we were interested in, he gave us keys to about 5 boats and told us to take a look and bring the keys back when we had made our choice. We didnt like how they olerated and left. All other boat sales we visited we were taken onto boats and all questions were answered while on the boat.
It took about two and a half years before we found the boat we bought. Dont be in a hurry to buy, make sure its the one you really want before you buy.