The U.K Parliament has voted to join the U.S. led coalition to eliminate NI-ISIS, but only in Iraq. The attacking of ISIS behind the sovereign territorial lines of the Syrian state was not a part of the U.K referendum request put forth by Prime Minister David Cameron.
Unlike President Obama – David Cameron understands the problematic approach of attacking an entity within Syria -without the approval of the Syrian government- as illegal. Indeed, by all international definitions, the incursions into Syria are both illegal and unauthorized.

…”I do believe there is a strong case for us to do more in Syria but I did not want to bring a motion to the house today which there wasnt consensus for”…  (David Cameron 9/26/14)

It is impossible to remain lawfully consistent against unauthorized Russian incursions into Ukraine, and simultaneously carryout the same activity into Syria. There is no structural context in U.S. or International Law which would permit such activity. Yet, Obama does it anyway.  [Prediction – Syria will be Libya 2.0]

UK Via Fox News – British lawmakers voted Friday to join the U.S.-led coalition and launch airstrikes on Islamic State group militants as early as this weekend in northern Iraq, but the motion did not endorse airstrikes in Syria.
Prime Minister David Cameron described the moves as critical to national security, arguing that facing down terrorists has become a matter of urgency.
“There isn’t a walk-on-by option; there isn’t an option hoping it will all go away,” he said.
He made a passionate plea that spelled out the consequences of inaction in drastic terms — noting that the militants had beheaded their victims, gouged out eyes and carried out crucifixions to promote goals from the “Dark Ages.”
The Independent newspaper reported that Cameron summed up ISIS fighters as, “psychopathic terrorists who want to kill us.”

The vote won easily, 524-43.
Earlier in the day, Belgium and Denmark also voted to join the coalition. American warplanes and drones hit Islamic State tanks, Humvees, checkpoints and bunkers Friday with aims to roll back and ultimately crush the Islamic State group.
Denmark said it would send seven F-16 fighter jets and 250 pilots and support staff, while Belgium will contribute six F-16s that are already en route to Jordan so they can go into action as early as Saturday.  (read more)