The normal set up is to connect your TV aerial to the Freeview box and its aerial outlet to the VCR with, in turn, the final TV aerial link from the VCR to the TV itself; the set top box's Scart lead goes to the VCR and a second Scart lead from the VCR to the television set's Scart AV socket.
Recording from the digital set top box may require some searching to find the correct channel - my set up uses the Satellite L1 or L2 channel (it's a 13-year-old VCR!).
The VCR can be used for normal terrestial recordings as normal (I.m working on the basis that your DVD recorder will be the equivalent of a normal VCR).
You'll probably find that a Scart switching box is more trouble than it's worth, especially if it's a manual version.