I live on the East Coast - last time I got something from the UK, it took 10 calendar days total which amazed me because I've had it take much longer.
Most sites say to give a UK to US shipment at least 21 days.

It can take much longer depending on how busy customs is - not sure if the holidays affect them like the regular mail, but I'd assume so.

Keep us posted - and hope you enjoy your new seeds.