Yes, spudfan, they were red and cream. The ones you describe, on the basis of what you've said, would indeed appear to be CIE ones. If they weren't, they wouldn't have been on rails. Where they were remains interesting; obviously it's on a disconnected siding adjacent to some station, as all CIE ones were. The prices given above in Jawfin's post indicate that they were not at all cheap! Bearing in mind that six full returns had to be bought too.... £7.10.0, or £7.50p, (equivalent to about €10 today) was about three weeks' wages to an ordinary working man. £12 was 50% more. Plus your fare.
When my family went to one in 1970 in North Wales (the British ones, incidentally, were green and cream), there were two adults and four children.... I have the receipt for it somewhere, must look it up. I think 1970 / 1971 was about the last year for the BR ones. I remember, incidentally, seeing Metro-Cammell railcars, and classes 47, 26 and (I think) 43's rattling past on long rakes of maroon Mk. 1's... (and some blue and grey ones!). We were just two years late for steam!