Hi Frank the Manc, a very warm welcome to the forum!
A few comments from me
We do like a laugh on here, but you will not be laughed at or sniggered at for making the odd, inevitable, dodgy newbie purchase!
Congratulations on choosing pre-decimal, both the Forum and the coins!
So you are thinking of concentrating on half crowns and crowns, will that be date runs (will be very expensive) or just different designs (I collect all the different designs (or 'types') for all silver denominations from Tudor to 1946)? How far back are you thinking of going? Just English coins?
Knowledge is the key, gained from experience, forums like this, and books. You will want an up-to-date price guide such as COLLECTORS' COINS GB 2015 (available http://www.predecimal.com/collectors-coins-2015-p-21018.html ), or Spink's Coins of England, and a book on grading, such as The Standard Guide to Grading British Coins: Pre-decimal Issues (1797 to 1970) just to start with. There are many other specialised books for when you get more into things.
It is always best to put pics up of both sides of the coin. From the reverse pic, your new purchase appears to be around Good Fine perhaps, and if the obverse is about the same then £16 is an ok price for it.
Try and buy the best example you can afford, you will not regret it in the long run
I'm sure there will be much more advice coming your way!