Severe loss of ranking after changing host and cannot find out why????

I've just been forced to change hosting company from an extremely poor service delivered by justhost.com in the US to a UK based service at vidahost. I only wish i had read the real reviews on the service from justhost and the amounts of server crashes and slowing they had before i went for them.

Anyway I had 3 seperate accounts/domains over at justhost which I transferred over to my new single account UK server along with the domain reg's.

Thing is now out of the two money sites I have one:

Home

has completely kept all its rankings, and I'm pritty sure a couple of keywords have gone up due to the improved speed and location

Though another site, which is older than the first and ranked #1 in google:

Steam Showers | Hot Tubs | Home Sauna | Whirlpool Baths | steamshower

has dropped to page 2 for the most searched terms (steam shower, steam showers) and completely gone for most our seconary words (steam bath, hot tub, whirlpool bath)

the thing is because this was just a straight transfer, so nothing has changed set up wise, there was no downtime ECT and the fact that the other site has kept ranking I'm really struggling to find why this has happened????

I wondered if anyone else has every experienced this fall when changing host?????