"I need to travel LHR-GLA rtn in Dec. There are very cheap return fares of £30 + tax available on the BA site. Will these accrue AA mileage? More importantly, will they accrue points for elite status, please?"
It depends on where your AA account is registered. If it is US/Canada/Mexico or Australia, it is fairly likely. It you are registered elsewhere in the world, then no. You will almost certainly be able to get a cheaper fare from AA.COM due to the £27.60 in taxes that the ba.com fare has. AA can do you a fare inclusive of taxes of $62.60 (£40 - £30 plus £10 taxes ) . Just look for the fare of $91.50 with BA. When you select it it will come up with a fare change and drop to $62.60
"As it's a RTW first class fare I'd like to take advantage of sitting at the front on the GLA route, if at all possible. "
There is only one class on domestic flights. If you can get it changed to be part of your RTW itinery, you will likely be booked in D class which will give you business class miles .
"Not even sure if they have a first class on this puddle jumper"
Dont get "1st" class within Europe really at all. The 2 classes of service are business and economy.
Dave