We spent 5 seasons sleeping in the awning annex and never used an inner tent. We just used Asda tab top curtains that slotted on the awning poles and then used a loose blackout/thermal lining secured with velcro to create an almost perfect blackout. Across the other end of the annex, where it meets the main awning we use longer curtains again just hung onto the poles with tab tops. Very snug and cosy and no problem with creepy crawlies. We were on a seasonal pitch so weight wasn't an issue.
Forgot to say I cut through the 'tabs' and put velcro on so the curtains could be put on after the awning was in place otherwise you have to loosen the poles to slot the curtains on.