ASIAN TREKKING - Well anything and everything you need including Mt Everest, specialist for your Chinese / Tibet Mountain Permits !
Perhaps most experienced in Nepal... or damn close. Nepal Treks | Treks in Nepal with Asian Trekking
SEA TO SUMMIT TREKKING - Trekking and Trekking peaks, and the easier 8000m Summits, very good staff.
HIGHLAND EXPEDITIONS - lowland treks ( 5000m and below ) and high pass crossings.
Used all and all good.... sorry got no other links.