Where?
If you have come to the UK from outside Europe, you have a fantastic opportunity to travel around during breaks from your studies. There are many online guides to help you choose where to go and which offer lots of advice about travelling. For example:
Rough Guide
Lonely Planet
When?
It's a good idea to plan as far as possible in advance. You will need to plan travel around your studies, you may need to obtain a travel visa and if you book travel in advance by rail or by air, prices tend to be cheaper. We strongly advise you not to take time out of your studies to travel. Your institution may have regulations against this and UK Border Force Officers may also question you on your return if you are travelling during term time (and not at the weekend).
If you need a visa to travel, embassies may require you to have three to six months left on your UK study visa so although you may have time at the end of your studies, it may be more difficult to travel outside the UK at that time. If you have a Tier 4 Student visa, you should be allowed to enter the UK if you return after the end date of your course and before your Tier 4 permission expires. This will depend on whether Border Force officials are satisfied when you enter the UK that you will either complete the activity you intend to carry out and leave the UK before your permission expires, or that you will submit an in-time application to extend your leave in the UK. You should carry any documentation relevant with you when you travel to show to the Border Force officer if required.
You may be able to obtain a letter from your institution confirming your graduation date if you travel between the end of your course and before your graduation.