What happens if I cancel the outbound of a round trip booking?
The routing is GVA-BRS/BRS-GVA, if anyone needs to know.
The reason is for a funeral which has been put a day earlier, which happens to be a few hours before I will arrive on the original booking.

My expectation is that it won't make the slightest bit of difference, because I believe that all easyJet flight bookings are treated as one way bookings, so a round trip booking is simply two one way bookings on the same booking reference. So in theory I shouldn't get my return segment (BRS-GVA) cancelled because of no show on the GVA-BRS. But I am submitting it to the hive intelligence here all the same.

The thing is, I find it is much cheaper to make a new booking than try and change the existing one.

If you cancel they won't refund. Just no show for GVA-BRS and claim taxes back.
Or move it
either way nothing will happen to the BRS-GVA

Bon, voil�, it doesn't even work if I try to do a dummy change of booking for GVA-BRS. The easyJet site is about as fit as everything to do with IT in Western Europe these days. It's impossible to select a different date, everything is greyed out, so a new separate booking it has to be. We're talking about early March here. So I just need to sure that it won't affect my ability to fly back to Geneva a few days later.

Right, just read your post after writing my latest one above. Certainly, they don't refund, unless it is within 24 hours (how reliable is that, by the way?)
For GVA-BRS I don't think that there will be all that much in the way of taxes. The flight cost CHF19.95 and one option was even available for CHF13.95.

Right, now it seems to work. Must have been some issue with just passing midnight here in Suisse Romande. So, the change fee is as follows, including CHF0 fare difference: CHF62.00. Obviously it is clearly advantageous to book a new one way for the wished for date (CHF16.95) and no-show for the current existing booking. It's silly, it never used to be like this, but I am no easyJet afficionado, really not (which means I hardly ever fly with them). The CHF62 (or GBP54) change fee is ridiculously high compared to what it used to be, just like the baggage fees have become.

I face a similar situation for BSL-IBZ-BSL next month, but with the difference that we are four people in one booking and only one person can’t fly the outbound segment BSL-IBZ. Does that make any difference if all the other three fly BSL-IBZ and we just book a new outbound for the fourth person?