While searching through the internet you can find several references dealing with the HMS Manica. Strangely enough, I couldn’t trace in the book Ships of the Royal Navy: the complete record of all fighting ships, by J.J. Colledge and Ben Warlow, published in 2006.
http://en.wikipedia.org/wiki/HMS_Manica doesn’t give more information than the ship was used in the Dardanelles campaign in 1915, mainly at the Anzac Cove to direct the gunfire. This source mentioned two comparable ships, namely the HMS Canning and the Hector. The most interesting of this website is the picture of the launching of a kite balloon from this ship while off Gallipoli in 1915; No. HU 66626 from the Imperial War Museum collection No. 9504-06.
At www.royalnavy.mod.uk you can upload a small document titled Fly Navy 100 which mentioned that the Manica was a tramp steamer fitted out by the RNAS Balloon section to be used as a kite balloon ship. She was sent towards the Dardanelles and used to give instructions through a telephone cable connected with the Manica, to direct the fire against the Turkish.
http://www.gallipoli-association.org/contentpage.asp?pageid=6 doesn’t give (directly) more information.
http://cas.awm.gov.au/photograph/A02028 Australian War Memorial, published a photo made in 1915 by an unknown photographer of the balloon ship HMS Monica off Anzac. Presumably this is a miswriting for Manica.
http://www.naval-history.net/xDKCas1917-05May.htm mentioned that Sunday 13 May 1917 on board of the ship the general servants James Barton (due to illness) and Edward H. Buckley died. Wednesday 16 May died the air mechanic Horace Thompson due to illness.
http://www.tayyareci.com/hvtarihi/canakkale/canak5.asp: “Because of the failure of allied air forces, a fixed balloon ship, weighed 3500 tons and named Manica, came to Dardanelles from England on March 22. On March 26, Serno and Schneider flew for reconnaissance and in the evening Schneider and Hüseyin Sedat repeated the reconnaissance and flew up to Limni. According to their report, it was understood that there would be no new naval attack. At the end of the same day, they returned to Istanbul.”
http://www.flightglobal.com/pdfarchive/view/1919/1919%20-%200579.html doesn’t give (directly) more information.
The most detailed information I found was in the book The Navy everywhere, published in 1919 by Conrad Cato, p. 144-145. He mentioned that she was an old tramp, ‘unloading manure from Australia…they proceeded to convert it to their needs, by fitting up a long sloping deck from forecastle to waist, fixing a dynamo to drive a hydrogen compressor, installing their winch and connecting it with the main engines, building a wireless telegraphy house, building quarters for officers and men, and generally adapting the fittings and appointments to what they conceived to be the requirements of a kite-balloon ship”. Her arrival at Lemnos was 16 April 1915 and within some days she saw actual service. Cato supplied much more information about her, mentioning for instance Turkish air attacks to destroy the ship.