Matthew Phillips has commented that his step-uncle complained about the change in pronunciation of this word in about 1990, blaming the BBC for the change. I thought it might be useful to look at the pronunciations given in a range of dictionaries over the years.
The OED’s 1st edition (this fascicle published in March 1918) gives two English pronunciations: /sɜːˈveɪləns/ and /sɜːˈveɪljəns/, and also the French pronunciation /syrvɛjɑ˜s/. The earliest quotation of the word’s use in English is from 1799, in italics, indicating its status as a perceived foreign word. Chambers’s Twentieth Century Dictionary, 1901, Routledge’s Pronouncing Dictionary, 1909, and my copy of the Nuttall edition of Walker’s Pronouncing Dictionary, which is undated, but must be from the early 20th century, all give the single pronunciation /sɜːˈveɪljəns/. These all pre-date the OED fascicle.
The earliest dictionary in my possession that gives /sɜːˈveɪəns/ is The New Universal Dictionary, edited by H T D Meredith, and published by Associated Newspapers. This is undated, but a feature in the appendix is a list of significant dates in British history, of which the last is the accession of Edward VIII, which closely dates the book to 1936, as his reign began in January that year, and ended in December.
The various current pronunciation dictionaries: Longman (LPD), Cambridge (formerly the Everyman) (EPD) and Oxford (ODP), all give /sɜːˈveɪləns/, LPD adds /sɜːˈveɪəns/, and EPD has /sɜːrˈveɪljəns/ as a US pronunciation.
As is so often the case, blaming the BBC for a change in linguistic usage is unwarranted.