€59 is is incredibly expensive for a dongle, unless the data costs are somehow subsidised. I have a dongle and it cost me about £20. I got an unlock code on the web in less than an hour. There are loads of free services offering this. In Croatia recently I got a local sim card for £11 and it gave me 1 gigabyte of data for a month. I was there over two weeks and didn't use it up!
If you go this route you sometimes need to enter a bit of mildly techie stuff such as APN settings, which tell the dongle which service it is using but you can obtain these on-line before you leave the U.K. and if you have to, enter them when you buy your local sim.
The best way to think of a dongle is that it is just like a mobile phone but without a speaker or microphone. You can access the web and even sent text messages but, when you put in a new sim card, the phone may need to know which provider its using and the provider's access details APN) may need to be entered into the dongle's settings.