Two quick question on compression fittings.

Firstly, I want to run a hot and cold water "main" across a room and put
in appropriate tees to feed the various items that will eventually be
fitted, the new toilet for example, however before I put the final
supply pipes in for these I would like to finish off other jobs in the
room, so would like to temporarily blank off their connection. Can I
use these (it is 15mm pipe work):

http://www.screwfix.com/prods/49888/...lank-Nut-2-Pk#

These are thread sealing, but compression tees are usually olive
sealing, does this matter or will they leak (obviously I will PTFE the
threads)?

Secondly, how do these work:

http://www.screwfix.com/prods/95682/...tting-22-15mm#

I can't understand what clamps the smaller pipe, as they aren't supplied
with any olives.

Thank you in advance for any help.