Ok, especially after what Paul has just said and considering my location , broadband down the phone line, at a slow pace (back of beyond) I suppose I should go for the external. what size, from what I can remember the hard drive on my computer is only 4gb.
They will be all much bigger than 4gb hence it's up to you to figure out what else you can store there. Bear in mind that photos these days are quite large and videos even larger. Also, having a new laptop might just open new horizons for you and start keeping/downloading more stuff.
I'm was advised to get anything bigger than 1TB with its own power supply. There are external drives that are only powered by the USB connection..... they are nice but maybe it's a good idea not to get one of those that is bigger than a 1TB.
Furthermore, you can buy a program such as Acronis and keep a backup of the whole laptop on the external drive..... if you ever get a virus or have another problem, you can get your laptop back in no time.... including operating system, Applications, configuration, and data.