yeh go for it mate, i usually dab in the morning, have some lunch and hit the thing in one set in the afternoon...
done loads like it, not had any comebacks... if the walls are roughish ti'll stay on..
obly thing you ever gotta worry bout with them things is this...
think of the abutment wall (where the conny joins the house)
thats an external wall...see the weepers they put in brickwork above ig/catnic lintels? theyre there to let water out that has soaked into the bricks, a cavity litel will channel water to the external face...
the wall above the conny is subject to ingress....
then if theres weepers above the french door in the conny, thats where the waters gonna come out (as well as the bricks)
the way round it is to install 'cavity trays' above the conny that work like a cavity lintel and channel the water back out again before it hits the 'internal' conny...
just dab it though mate, everybody else will...
if not theyll hardwall it, which i think is even worse on the abutment wall...