Neither Philips nor SmartThings officially support using the Hue dimmer switch with SmartThings, but there are some community members who have created a custom device type handler that you can try. It’s not working consistently for everyone, but you could ask more questions in the authors thread to see if you want to try it.
Whenever you are looking for community – created code, you will probably find it the fastest by starting with the quick browse lists in the community – created wiki.
In this case, look in the device type handler section for the “lighting” list, and you will find an entry marked “Alpha” for the Hue dimmer ZHA. That’s the one you want to try.
(Also note that if you do use the dimmer switch in this way, it will no longer be connected to your hue bridge and you won’t be able to use it except through SmartThings.)
If you’d like to look at any alternative devices which might work more easily, take a look at the buttons and remotes FAQ. Each entry is marked with the region, so it’s pretty easy to find the ones that are available in the UK.