BALLYHILL prior to her lengthening in 1963. Jabegren, you are quite correct that their appearance was reminescent of the 1930's, only the funnels got shorter and fatter, but she really was built in 1954. Kelly's continued in the fifties to build very similar vessels with the BALLYLUMFORD (54), BALLYMENA (54), BALLYLAGAN, (55) and even the later and bigger BALLYLORAN (58), BALLYLESSON (59), BALLYRUSH (62) and BALLYRORY (63) were not too dis-similar. Regarding the lack of radar, I heard it said that all their captains knew the Irish Sea like the back of their hands and in a fog they only had to step onto the bridge wing, take a sniff to know where they were.
Very many coasting vessels did not have radar into the 1960s. Many continued to stream the patent log and as commented, knew the sea routes in the same way that you do not need a map to go to the supermarket. Fog, or severe weather, was the big problem and coasters and fishing vessels did lose their position, often with tragic results.
With regard to design, owners and shipbuilders in UK were very reluctant to go for things new, in the end to their detriment.