Thanks everyone for all the replies and info, the bike set up is shimano 105 2x11, hydraulic brakes.

so i assumed a 105 drop shifter would be compatible with dérailleurs brakes etc ? But was doubting myself when I read that break calipers may also be an issue as I had no idea why that would be so.

I have that bike which I upgraded from its aluminium carbon forked ancestor the fastroad sl1.
Which I also still have plus I've a run around trek fx 2

So I don't really want to buy another bike and I feel if lose to much selling the carbon advanced and would end up with an inferior bike.

Hard to sell anything at the moment, i had the sl1 up for sale but didn't even get an offer at half price on a 1 year old bike in pristine condition.

The issue with my ergon gp5 is they make the handle bar wider than if like even after taking 10mm off each end, and I find if I use the side grips my hands are angled left and right slightly from my wrists and I can't shorten the bar and further .

so if it was just a case of handlebar, shifters, brake lines, bar tape , adjustable stem I'd probably consider it worth it , but if I had to change dérailleurs and calipers as well if say , too much