Found in my late Aunt's possessions. Photograph of unidentified uniform:
It looks, with the tapering frogging connecting at the single, center row of buttons, you may have a Royal Horse Artillery uniform. Some better images can be seem on a forum here. Another forum has this image. (note similar positioning of the aiguillette). (Note the feature I identified as an aiguillette may also be described in this case as a busby line, cap line or body line. See (commercial site) here.
Another more detailed image of a similar uniform jacket can be found at Museums Victoria Collections labeled as 'Jacket - Victorian Horse Artillery, Full Dress, circa 1890' :
Concerning the medals, they would appear to be Campaign Medals. However without color or a more precise time frame they are difficult to match.
He is indeed Royal Horse Artillery as has been suggested. The medal ribbons appear to be those of the Queen’s and King’s South Africa medals (of Victoria and Edward VII respectively), that were awarded for the 2nd Anglo/Boer War 1899-1902. They date the photo to before WW1.