Finding vegetarian food in Scotland is not too much of a challenge. In many ways it is easier here than in many, and possibly most other countries.  When searching for products in grocery stores, vegetarian products will be listed with a V on them.  There are also extensive lines of fake meat products, one major one called Quorn, which are available in the larger grocery stores as well as the smaller, convienience stores. 

Most restaurants in Scotland also make sure to have a vegetarian option on their menu, if not a few.  If you come across a restaurant without a vegetarian option, don't hesitate to ask since it is expected that restaurants will cater to vegetarians.  However - after spending a while in Scotland, you may tire of Macaroni and Cheese or veggie burgers, as many restaurants don't feel the need to vary the menu much beyond that for vegetarians. 

You can also find vegetarian haggis available in stores, and some restaurants, so be sure to give it a try.