Going on from R W Stewart, I found him in the London Gazette 1890 stating the following:
Staff, Colonel R. W. Stewart, from Lieutenant-
Colonel, half-pay, Royal Engineers, to be a
Colonel on the Staff for Royal Engineers, and
to have the substantive rank of Colonel in the
Army, vice Major-General E. O. Hewett,
C.M.G., Royal Engineers, who vacated that
appointment on promotion. Dated 1st July,
1890.

I will need to send you the article as it's pdf and not GED or JPG that's accepted here to attach...:(

I also saw something about the Prince of Wales Own West Yorkshire regiment mentioned later in this same article and was advised recently, of course word of mouth at this stage that and I quote: "It was rumoured that [Wilfred Stephens had] the aid of the Prince of Wales. Acting Aid de comp when he was here."

I am unsure if the PWO Wst Yorkshire regiment went to Fiji but if so this maybe where Wilfred, if our Wilfred doesn't come from Yorkshire, may have been confused as coming from Yorkshire due to belonging to this regiment. No proof that he was part of this regiment or that this regiment had any association with the creating of the new capital of Fiji, being Suva. Just a thought.

It was also advised to me from memories of the eldest person associated in Fiji with the Stephens family is:

"[Wilfred Stephens] came to Fiji as a Royal Engineer with three others, the names...remember[ed] are Wilson, Lazarus not sure of spelling of lazaras – Campbell maybe?.
Descendants of Wilson and Stephens are still here. Lazarus did not marry here in Fiji. . . [and] Campbell. . . settled in the Yasawa’s.

I'm sooo loving all the information you have come across and sooo thankful for your time and effort..it helps paint a picture and gives some sort of timeline and stronger link to the Wilfred Stephens I have found in England...the only one that's making sense.