One good purchase, if you intend to keep on modelling is a cutting mat. In this case it comes from a modelling tool kit by Faller, which my wife brought me as a gift. It is A4 sized and self-healing. Have a look for one down at your local hobby supplies or modelling shop. You should be able to pick one up for small money.
Usually the have some grid pattern and guide lines on them and can be used not only for modelling but als other arts and crafts which involve cutting.
They are a great investment when it comes to protect your worktop. An additional feature on most available mats is that they are “self-healing” which means that the cuts disappear.

A4 size Cutting Mat