I don't know whether you are still looking but I only just found your post. The Jane Sibbald you mention married my GGGrand-uncle William Edward Harvey and I have the following notes re her father William on my tree which might be of interest though they're not specifically about Ceylon;
Obit in Association medical journal;
"Sibbald, William, M.D., at Maidstone, aged 63, on February 15th. Dr. Sibbald graduated at Edinburgh in 1809, and in August 1810, entered the medical department of the army. During the campaigns of 1813 and 1814, he served in the Peninsula, being present at the battles of Orthes and Tou
louse. In June 1814, he accompanied the expedition to New Orleans; and on his return in 1815, joined the army at Brussels, soon after the battle of Waterloo. In this year he became Staff-Surgeon. In 1817, he went to the Mauritius; and, after a few years, he proceeded on promotion as Deputy Assistant-Inspector to Ceylon. On retiring, in July 1833, with the rank of Physician to the Forces, he settled at Maidstone; and was soon afterwards appointed Physician to the West Kent Infirmary, the duties of which office he discharged till a week before his death. He was also Visiting Physician to the Kent County Lunatic Asylum, and Consulting Physician to the Kent Ophthalmic Hospital at Maidstone. He had received the war medal with three clasps."
'The Asiatic journal and monthly miscellany, Volume 6 By East India Company' says he arrived with his wife on March 18, 1818 having left the Cape on January 25th.
I'm fascinated by the widowed Jane's 1871 census which appears to have her living with a painter and his wife, a pianist and composer, an author and his wife, and a visitor with no occupation and a servant, apparently all as a single household, one of several at the same address. It sounds positively Bohemiam, especially for a vicar's widow.
Jane's MI in the Church of the Blessed Mary, Walmer, Kent, England reads;
'M of William Harvey, Priest, M.A. Oxon.Youngest son of Sir Thomas Harvey K.C.B. Vice Admiral of the White, died March 18th 1865 aged 41 years and of Jane his wife, died December 7th 1891 aged 66 years. Both are buried in this churchyard and also of their children William, Flag Lieutenant H.M.S. Bellerophon, died at Halifax N.S. October 13th 1879 aged 28 years. Henry Nowell, Barrister at Law, Middle Temple. Died December 22nd 1828 aged 76 years. Helen Jane died April 1st 1877 aged 23 years. Alice Maude wife of John Richard Statham died January 30th 1945 aged 87 years'
PS Just seen that William Sibbald was "Surgeon to the forces in the Isle of France" [ie. Mauritius] when he wed in 1817. Blackwood's magazine, Oct.1817, p.126. So perhaps he came back to London to wed, or was given the job title and married before actually going to Mauritius.