BJCM double accessories, advice needed please.

[notso]

Have ordered BJCM double for 21 month old and 5 month old boys, have a couple of questions about accessories.

I am thinking of buying the carrycot second hand unless boots get theres back in stock but is it worth it for a couple of months use?

Can you get a raincover to cover just one side? DS2 prefers to take his chances with a waterproof all-in-one and hates being covered but DS3 will need some protection from the welsh elements.

Can you use two single bumper bars or just the double one?

Are any of the other accessories worth a look?
TIA

Grr theirs not theres sorry.

I wouldn't bother with a carrycot for a 5 month old. Simply use the seat laid flat with a footmuff or blanket or even nothing!
There is one long bumper bar.

Thanks Tiggy.
Have ordered the bumper bar.