So someone like SKY will have no DSLAM or use a DSLAM?
Depends upon the product.
For
ADSL, being MPF LLU they have their own MSANs in the local exchange. Everything goes over Openreach copper to the MDF in the exchange.
A Handover Frame passes voice and data over to the LLU MSAN and traffic then goes via their backhaul - See
LLU Handover Frames. There's photos on that page of the Handover Frames & the Optical Fibre Distribution Frame Cabinet.
For
VDSL the DSLAM is in the FTTC cab so belongs to Openreach and all the
DMT stuff such as sync etc is done there.
Data from the cab goes back to the headend exchange (which may not be the local one) to the Openreach OLT. From here the SP can purchase GEA cablelink connectivity to hook up to their backhaul.
Any voice telephony is as normal from the PCP to the MDF at the local exchange. - See
How FTTC works