marshyc: I made the same mistake. Still got one T5 Neo from warden_jp and it's like a dim blue.
Thing is, after the UltraLEDs in the front, and bearing in mind that the bulb fits at 90 degs in the lamp holder, I've decided to do something a little different - solder in a direct LED assembly. I've only just ordered the parts (in the last 5 minutes) so I'll let you know how it goes.
I'm also having the same issue with the LED wedge bulbs for side lights; they're slightly too blue against the Xenonmax H7s I have. They're
these from UltraLEDs. Which ones did you try that were a little too yellow? They might work quite well with the Xenonmax bulbs.