Janine2020

@Dee 
Think the initial confusion was using the word 'sovereign' in your initial post. I know what you meant, although a 'sovereign' refers to a particular UK gold coin as others mentioned above. I assume that you were referring to silver coins that were also minted as a currency, by a National mint, etc.
With silver coins you need to consider the 'spot' price of the metal itself (currently around £14.50 per ounce) plus the 'premium' on top of that which is essentially the cost of getting the metal, melting it, making into nice shiny coins, and distributing - this is why a one ounce coin won't be for sale at £14.50.  Then there is the 'numismatic' value, which refers to another type of premium based on the desirability of the coin among collectors/buyers.
a) So one ounce of pure silver, in isolation, should cost £14.50.
b) A generic one ounce silver coin with no particular collectible value seems to currently be available for around £20 (or spot + 38% premium)
c) A rare, perfect condition one ounce silver proof coin from a hundred-odd years ago might cost (these figures as an example only) £50 (or spot + 245% numismatic premium)
Stackers like to buy (b), collectors like to buy (c), and everyone would like to buy (a) but generally can't.
There's loads to it, I'm new to it myself - the buy/sell pages will give you an idea of roughly what stuff should cost.
To answer a couple of the specific questions you ask though:
The generic coins (what I think you meant by 'sovereign') that you're best looking at are: silver Brittanias, Canadian Maple Leaf, Krugerrand, Philharmonics, and maybe American Silver Eagles.  I'm sure there are others but these seem to be the most common, and usually have the lowest premiums at traders. They're popular & common and so have little numismatic premium (though some years did have low mintages, which would change this fact, but that's one to read up on.)
Where to buy - the forum selling threads are first stop, as you're likely to find some nice deals and won't have to wait long for delivery if the seller is also here in the UK with you. If you do buy from online traders, don't buy silver from UK-based dealers as you have to pay VAT.  There are European dealers from whom you can buy without paying UK VAT. I don't really study tax law, but I understand that this is totally above board and isn't the same as 'avoiding tax'.  Obviously, the delivery charge would make this a bad deal for small purchases, usually between £9 and £12 (in my experience) for a small package.
The general advice here seems to be to avoid eBay unless you are very confidant in the seller. there are plenty of fakes (less so with silver than gold, but still) and the seller will be paying eBay fees on the sale. This means that they are making enough on the sale to cover those fees, and so you're likely to pay over the odds. Of course, there ARE reputable sellers and good deals on there too, but just tread carefully.

A Sov a month sounds good, and at the cheapest possible price is 👌. Buy it from a good source which can also include this forum. 
 
Good strategy if you ask me. 
Fellow forums member has built up a comparison site.
http://goldprice.eu5.net/