Hi foghorn, sorry for the mid-ident!
129.55 is Luton Radar (or Approach, if you prefer), 128.75 Luton Director.
The route Woburn-BPK is one we are very use to, and we use to be quite happy putting VFR traffic over the landing threshold at 2,500ft, knowing that any go-arounds would (or should!) only go to 2,000ft. But with the go-around procedures being revised to go to 3,000ft, we either have to put transit traffic up to 3,500ft, or invite you go 8nm east or west. If there is no landing traffic then there is no problem.
If you are IFR (or SVFR) then I am afraid it will mean less chance of a zone transit as we have to provide standard separation with our own IFR traffic. 1,000ft against the go-around would mean 4,000ft over the top which we cannot do with transit traffic, hence you'll get vectored to provide radar separation. And if the boys and girls are busy with inbounds then wouldn't want to do it.
But we are not busy all of the time so zone transits should not become any different to what we do now.
Hope this helps.