Tvheadend

806 services on Freeview seems like a lot... I have 170 services on 9 muxes here. That aside, it'd be impossible for anyone except you to decide what "the major channels" actually are, I think. For example, I might really like news and late-night gambling/soft porn channels, but care nothing for documentaries; alternatively, I may think that ITV is, in general, a waste of bandwidth and should be suppressed if possible. And one of those scenarios is actually true...

What I've done is simply define a new tag, and then tagged the channels that I use most (for me, the mainstream HD channels from -T and -S) into that group. You can then simply use that tag in both the web interface and Kodi to significantly shorten the list of extraneous stuff that's of no interest. It can't help when channels switch over to Teleshopping, but it does work correctly when the channel identifier changes on a time-shared basis (e.g. CBBC and BBC Four or whatever the pairing is).

My list runs to 17 pages of 50 entries. The first two pages are largely unallocated services. Then there are multiple entries for many services. BBC 1 for example has six entries on different frequencies.

I would class the major channels as BBC 1 and 2, ITV, channel 4, Channel 5 and film 4.

But this misses the point. What ever you want to watch, it is likely to be a small subset of available channels, so starting from none would be better than starting from all enabled even with 170 services.