hi CJ mate.. your right on your dryin times . on average its usualy 30 days...
If you want to tile earlier then you can use the schluter ditra system as this will allow the screed to dry out from underneath the mat... Or you could use bal green screed adhesive which i think is your best option as it will be cheaper than ditra....heres a link for bal green screed tech info.............dave.....
Green Screed Adhesive
p.s. there is also a commission period before you should turn the UFH on so check with bal before you allow customer to turn it on.....