Which model of Hue switches are you using?
There are a couple of plug-in pocket sockets which work with the hue bridge and then appear as a controllable smart bulb to SmartThings, so that’s probably the simplest option. Osram’s Smart+ Lightify line has both an indoor and an outdoor model which would work. Shop around: you should be able to find them for about £25.
(Note to US members: Osram is a German company, and although their Sylvania Brand is available in the US, I believe the pocket sockets that work with a hue bridge are currently only available in the EU. They have other pocket sockets sold for the US market, but those connect directly to smartthings, not to the hue bridge. )
Innr also has a pocket socket that should work, but it’s not available at as many places. List price is around £30, but it can often be found for less.
The IKEA Plug works with SmartThings, but not with the Hue Bridge
The IKEA Tradfri pocket sockets are less expensive and can connect directly to smartthings as @Steveuk23 mentioned, I’m just not sure if they will also work with SmartThings through the Hue bridge or not. That’s why I asked what model number of switches you are using.
edited to update
According to the Reddit Tradfri forum, including some postings by IKEA staff, the Tradfri outlet is not recognized by the Hue bridge at this time.