Sylfaen on WinXP has W, Y with acute, grave, dieresis, and circumflex and it comes on Windows or in Office. It was designed by John Hudaon, who has some connection with Wales and Geraldine Wade who is from Wales. So if you have a Windows machine the .ttf will load on OSX.

Sylfaen was designed for Microsoft in 1998 by John Hudson and W. Ross Mills of Tiro Typeworks, and Geraldine Wade of Monotype Typography. Sylfaen is a Welsh word meaning "foundation"; an apt name since the font stemmed from research into the typographic requirements of many different scripts and languages.

This version of Sylfaen supports the WGL4.0 character set, for Pan-European language coverage. In addition to Latin, Greek and Cyrillic letterforms, the font contains the characters necessary for support of the Armenian and Georgian languages.

and thet's the description in the font.

The only limitation of Sylfaen is that it exists only in a single weight and style: no italic, no bold, etc. This is because it was originally made for a research project, and not intended to be shipped.

The Welsh diacritic characters you need are available in all the Windows core fonts, including Times New Roman, Arial, etc. and also Palatino Linotype, Georgia, Verdana, etc.

They're available in core MacOS X fonts too, but I was hoping to have a wider choice really.

Several of Adobe's type families support "extended Latin" which includes Welsh. Minion Pro and warnock Pro are among those which do (also Myriad Pro and Sava Pro, which are not likely to be of interest for this purpose).

Additionally, a number of the typefaces we expect to release in the next 6-8 months will also have such support.

Regards,

T