Seeing as it's fitted with 2 RCDs (DP and rated the same as the main switch) is it acceptable to simply remove the switch and feed the first RCD from the tails?
no, because you would then not have a single isolator for the whole installation, or you would have 2 RCDs in series, depending how you configured the DB.
you could remove 1 RCD completely and replace it's set of MCBs with RCBOs. that will give you 2 spare ways. might be cheaper to fit a bigger Dual RCD board though.
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc