Wylex, Crabtree & Volex brands are all part of the Electrium group..
But not 100% sure who/what/where the Sector brand is/was part off.
Although as UNG suggests other googling does suggests they were Rexel-Senate own brand, possibly manufactured by Wylex?
In my box of old tat I have a Sector MCB..
which if compared with a Volex & Wylex MCB there are both similarities and slight differences in the casings, terminal connections, toggle switches..
From my random sample the Sector MCB looks a bit more like the Volex rather than the Wylex...
However we do also know that not even the same manufactures products always keep their external dimensions un-altered!
No idea what how the RCD's may or may not differ..?
But if they have any "L" or "N" designations printed on them that could affect what may or may not be a suitable replacement.?
i.e. Left-hand -vs- Right-hand main switch position..
e.g. Wylex & Volex main switches are very similar but have "N" marked on opposite terminals!
Personally I tend to find it un-economically viable for me to spend time trying to track down an obsolete product for any customers..
And I don't supply or fit second-hand equipment without any manufactures warranties...
So if a google can't locate a suitable new product relatively quickly it becomes too much hassle for minimal return...
Just tell them the truth..
That their CU is from an obsolete manufacture who you cannot get replacement parts for anymore, so just as with any other products, (Washing machine, Vacuum cleaner, TV, Coffee maker etc.. etc.. etc.. ) if you can no longer get parts you either put up with what you currently have or replace it!