Going via Heathrow just so you can use the 241 doesn't make sense to me. You have to book round trip (assuming itis anChase 241) which makes it nearly impossible, especially in First.

If you have enough Alaska miles you can use those to go SEa to LAX and then LAX tomAustralia (SYD, MEL, or BNE) on Qantas. I saw a seat in First yesterday for the MEL flight for a date in early April. And quite a few award seats in J. The Alaska website is very easy to use ( easier than BA) but watch out for "mixed cabin" routes.

We are going to Sydney next January in QF First with our Alaska miles, and coming home in J with our BA miles.