A NOSTALGIC reunion of former Gurkhas with their old Hong Kong base has been scuppered by the choice of management firm for the moth-balled military sites. Tenders to provide property management and security for the bases made vacant by the withdrawal of the British Garrison have been awarded to First Pacific Davies and Urban Property Management Limited. Jardine Securicor Gurkha Services, whose security guards are all former Gurkhas who once served in the territory, lost out. Had its tender been accepted by the Government Property Agency, it would have paved the way for Gurkhas to have patrolled their former base at Gallipoli Lines near Fanling. The base was the first military site to become vacant last month when the 3rd Royal Gurkha Rifles - formerly the 10th Gurkha Rifles - went to Britain. ''It's a shame,'' said managing director Chris Hardy. ''It would have been fitting to have had the Gurkhas guarding their old base.'' The Government split the sites - some destined for the People's Liberation Army and others whose futures are yet to be decided - into two groups of nine and invited private-sector tenders. Urban Property Management will provide security and management of sites including Gallipoli Lines, Perowne Barracks and So Kon Po and Mission Road sports grounds with First Pacific Davies looking after sites including Stanley Fort. Responsibilities include security, cleaning and general maintenance, but repairs will be left in the hands of the Government. The estimated $35 million annual cost of maintaining the sites will be partially recovered by the Government leasing certain land within the sites during the next few years. The bulk of the revenue could be generated by leasing military accommodation. ''It is a very unusual brief and a great opportunity for the company to work with the Hong Kong Government in relation to the eventual draw-down in 1997,'' said First Pacific Davies chairman David Davies.