I have an original stake in a wallet with the keys, but I've never managed to get the client working on my Mac or PC. Is there a way to access them without having to install the Client? Not sure what to do with the files downloaded from Github. As you can tell I don't really know what I'm doing, but would like to access the coins.
Try the lightwallet. Can't do much wrong there
http://bob.nem.ninja/lightwallet-standalone-1.7-cdn-nginx1.8.zip .
You can also try
http://bob.nem.ninja:7777 but it's recommended to run it locally for security reasons. bob is a node run by a dev though so you should be fine there.
Thanks, seem to have Lighwallet running, and I've read the tutorial on the site, am I meant to choose one of the hosts or use the custom node? Not sure what the different host names represent.
I guess it's best for you to choose one of the listed hosts. Try to stick with the same host because local storage (which is where your wallet will be stored) works on a per domain basis. So if you switch host you're gonna have to re-create the wallet (which isn't a big deal so long as you have the priv-key and/or password handy).