The shunt button you're thinking of is probably the little jumpers inside on a separate board that allow you to pick what frequencies you want to run. You can choose from CON which is 10 meter only, CON 2 which is 10 meter plus you have to push 2 buttons to get it to 11 meters, CON 3 which does all of the band from 26.5 (I think) to 29.7 (I think) but doesn't allow you to work 10 meter repeaters, or if you just want to stay on the CB portion (like no one does) you pick CON 4.
In the beginning all of the Magnum S45's as well as the 257's came with the jumpers. However some radios recently began coming out of the factory with the shunts cut off flush with the board in an attempt (guessing from the FCC) to keep people from easily converting them to run on the 11 meter citizens band, since they do not meet FCC standards, plus they do more than 4 watts of power, and can cover multiple frequencies outside of 26.965 and 27.405 MHz. Then again I see you're in Ireland so maybe things are different.
But even with the posts cut down to the board, it's nothing a little blob of solder can't fix. But yes all the jumpers are, are 4 sets of little posts that stick up that essentially have a piece of wire ran across the posts. With the posts trimmed down, you'll have to pick up the solder iron and some solder to connect the posts.
It's really easy to do the mod, but if you don't feel comfortable, you'll have to find someone who is.