Ok I've downloaded Electrum and put the wallet address I sent the coins to and they have appeared in there. I'm not sure what I do next though, do I need to use the private key from my sending account, or the receiving Ledger wallet? the sending is through Coinbase so I'm not sure how I even got about getting the private key from there (if at all available)
Click on receive in Ledger. You should get a bitcoin address. Copy this and paste into Electrum "Pay to" box. Send the amount from Electrum and you should receive it instantly in your Ledger. Do not mess with the private keys.
Ok thanks i'll try that. Does it matter that the wallet address changes each time and doesn't match up with where the initial transaction was sent?
No. Address changes every time in order to ensure a better privacy to your coins. Re using the same address although it can be done is never recommended from almost all big major wallets, that's why Ledger for example changes address every time you request payment.
So by using a different address to send from the wathing wallet in Electrum, should still be able to recognise that the private key related to that wallet is right, and then transfer them to my Ledger? Sorry I'm new to this and pretty worried i've lost the 1.4 BTC I bought two days ago..!
If its a watching only wallet then you need to import the private key of that address to another wallet which operates normally. Now clarify me things as you are confusing me a bit.
1. This 1.4 Btc you bought two days ago to which wallet did you transfer them and I need to see the transaction ID of such transfer.
If you want to send from the watch only wallet, then here is the guide on how to do it and transfer your amount of bitcoins from your watch only wallet to Ledger Nano S.
http://docs.electrum.org/en/latest/coldstorage.html#create-a-watching-only-version-of-your-walletAnd I don't understand why you need a watch only wallet when you have a hardware one ?