Sure this is a total no brainer, but doesn't hurt to be told that!

Need a flight to dubai in around 4-6 weeks time, min of prem ecconomy.

BA yesterday/today is showing a shade under 770 + 20k miles to upgrade
Silverjet has a sale price of 880 (+5% back via quidco and 5% discount code)

so essentially, identical fares.

Tier points arent too much use - wont make the threshold this year.

Worth a try in Silverjet? What's the valet service like? - having images of the valet service that was on watchdog a while back!

Cheers!