I used to keep pet rats a few years ago over a period of about ten years so learnt a lot about them by reading several books and learning how to achieve confidence in training them and I can tell you that they are very intelligent creatures. However, they can be trained by one method only and that is with small food treats and it is fact that if they enter a maze of walls it takes very little training for them to find their next meal. Although wild rats live in a totally different environment to their domestic cousins their thinking ability is very much identical but one thing is for sure and that is they don't like human contact unless they have been trained from an early age. Because wild rats and mice have no human contact they are actually petrified of us but the only time they are ever likely to enter your tent is a) when you are absent and b) when food is left easily available for them to steal as they are very clever sneak thieves and can snatch food in the blink of an eye. It's also an old wives tale that mice like cheese as they are more likely to go for bread and any sweet things such as jam or honey. So to answer your question, mice or rats will totally avoid you at all costs unless you leave any unwrapped or discarded food about as they really have no interest in anything else apart from keeping warm and dry.
Having experience of them myself you would think I would be more cautious but even I got caught out a few years ago when I found mouse droppings in my caravan when left in storage. I had only gone and left a shoe box with paper in under the caravan seat and found that mice had chewed a hole as the side as their front door, but where was the food source? Blimey! they had only managed to find A couple of unused doggy chew sticks in another low down cupboard so basically they were keeping warm living in 5 star luxury. I've not had a problem with them since though as I discarded the box and remove any doggy chew sticks when leaving the caravan but now use a sonic rodent repeller as well which has worked successfully for the past 4 years.
Don't be afraid of camping because of mice or rats as they are a hell of a lot more frightened than what you are.
Thank you everyone for your replies, I wouldn't let it stop me camping! Unless I woke in the night to see one sitting on my bed or something :-0 then I may consider never going again!! Haha.
But if it's unlikely/ rare then I will put it to the back of my mind and worry about something else! Spiders!! Now I know I'm bonus to come across my fair share of those?? Right?
Oh well, don't like them much but I really want to go camping. Seen a lot of reviews on pepermint, creepy crawlies and rodents aparently can't stand the smell so I may make my own spray and spray it around the outside of the tent (don't want to wet the inside do I?) just incase ;-).... Then I will put it to the back of my mind, a large hot Choc and baileys (or 5) might help :-)
Camping on the Isle of Purbeck a few weeks ago, mice ate holes in my pouch of lentils, my bag of porridge oats and finished off by chewing holes in an irreplaceable T-shirt.
As I was packing up, a mouse ran into my tent and hid in a corner making itself at home, much to the delight of onlooking children ("catch it, catch it!").