You could install w_scan and get the frequency from that, then just use that and 8mz with everything else on auto in tvh setup. The HD mux carries details for all the others but the SD muxes don't carry details for the HD mux.
I have a 290e and it works OK with tvh for me.
Another way would be to use - http://www.digitaluk.co.uk/coveragechecker/main/index/dummy/NA/yes
But that gives channel numbers, to convert -
For channel number N frequency in Hz =
(306 + (N x 8)) x 1000000
If the channel number has a + or - after it add/subtract 167000