So after seeing a post on reddit, i downloaded and installed it as per the thread and it's worked!
Below is the reddit thread and what the OP said to do. as stated above, it works for me.
REMEMBER TO MAKE A BACKUP OF YOUR CACHE FIRSTSo for all the people that are frustrated with the slow download from Jagex, I've compressed the cache files and uploaded them all to my google drive. I'm only really posting this because my friend suggested this for all the people having problems on here, since he had been complaining all day.
https://drive.google.com/open?id=0B6x63hLYFo2jdVJmZlZObG1RQ0kThe default location for the cache files are in
C:\ProgramData\Jagex\RuneScape
Just decompress the folder after downloading it and copy it over. Do note you need to not be running the NXT client so it can overwrite the files.
Edit: SHA-256 Checksum for the compressed file:
11FE42B066CF698B4081E95E8E8FAA69BC4E2F70D37D2ECB23A2F63AC0EFD08F