With the OP being quoted "over 10,000GBP" for the part alone, this is a whole new level of dealership scalpery! Even if shipping and taxes adds another £1K, that's a ridiculous mark-up.
The part would no doubt have to be specially ordered from Japan anyway, so it's not like the Lexus dealer would get one any quicker.
Anyway, yes can recommend Amayama. Always great service when I've used them. 👍