not trying to 'convince' anyone...but its common knowledge
go to fivetens site and click on any pair of shoes, under the photo will be a little blurb concerning what stealth compound was used.
also common knowledge: the c4 compound is the ORIGINAL stealth rubber, the only rubber rock climbers are after when they get a resole..it is the most tried & true as far as pure traction.
these days they make climbing shoes with a bunch of different compounds, but these all have slightly different focuses IE durability, stiffness in the toe/midsole areas, shock absorption for day long multipitch routes, etc.
as far as i know, the guide tennies are the only approach shoes that come with the c4 compound. not that it matters, as you can get any pair of shoes you want resoled with c4. take them to a climbing shoe cobbler and be done with it...im very into bouldering as well, and know there is a very hearty bouldering scene in the UK..you should have no trouble finding one near you!