Alex - £35 equates to about $50 US, and I believe
DCL is at $65. Personally, I do not mind the extra cost per person (though there is only two in our party). I do not begrudge anyone making a profit for their time, energy and efforts, and DCL knows where to find us, should there be ANY issues. If we disappear, and are never heard from again, DCL knows where to send the search parties.
I like that we did not have to spend any time researching a 3rd party tour company. In addition, if there are ANY issues, we have a much better chance at getting refunds or credits. Last year, we had a DCL excursion from Tortola to Jost VanDyke Island. The vendor did not put out the water activities at the proper time (water slide & bounce). When we returned to the ship, we had a notice in our stateroom indicting we were being provided a $15 credit.
Hopefully, all excursions will go as planned - without incidents, and all will be happy.