I have also read there may be some other coins generated by having Bitcoin can anyone tell me more about this please, if I’m likely to have these and how to get to them?
If you acquired your Bitcoin in December 2017, you don't have any of the Forkcoins that are worth pursuing. The valuable ones forked a few months earlier.
However, holding bitcoins in a paper wallet isn't that recommended, IMO, since there are far better solutions. For instance,
Electrum allows you to access as many addresses as you want instead of one (with paper wallet), which means better privacy and alongside, you only need to write down twelve words instead of a private key which you can write it improperly.
A properly generated Bitcoin paper wallet is considered cold storage, which is much safer than installing Electrum on an online system. Both can be used, depending on among others the amount you're storing.
is it ok to type my cold wallets key onto an online site?
NEVER do that!
I mean what would have happened if my friend that helped me had taken a picture of that paper wallet on his phone
Anyone who knows your private key can take your funds anytime they want.
I also think I have some empty paper wallets so I need to tidy up.
Just in case: I wouldn't start throwing out paper wallets. Use a pen to write for instance "empty" on them, but keep it nonetheless.
One of the safest ways to transfer funds out of cold storage is by
signing the transaction offline.
Also I would like to buy some more slowly so maybe add each month with £50 or £100 each month.
Buying and keeping it on an exchange works fine for small amounts, but long-term, I wouldn't trust third parties. However, exchanges usually charge quite large withdrawal fees, and monthly withdrawing small amounts of Bitcoin will lead to
large transaction fees if you ever want to use them. Nothing you can't overcome, but it's good to realize the limitations beforehand.
If you're going for a hardware wallet, they usually have better offers on Black Friday.