Mice are gorgeous.. as long as they dont find a way from your loft to your kitchen where they will walk all over the worktops leaving droppings and urine everywhere they go. All your food will have to be in mouseproof containers and they can get through the smallest gaps.
When my new bedroom was constructed in the garage I invaded their space.. and boy did they let me know.. they ran all over my bedroom.. all over my clothes.. every single item of which had to be washed or cleaned.
Lovely though they are the can very soon grow to be a problem .. and if you dont want Gizmo (my chihuahua is gizmo) to present you with gifts on a regular basis dont encourage the meece!
Best of luck
jaki