Hi
Rhosboeth's co-ordinates are correct. Mountaineers will be more familiar with the form SH482569 (6 figure reference). Haven't checked postcode, know LL54 7 bit is correct.
Although my family is from Porthmadog area, one of my mother's sisters married one of the sons of Gilwern Isaf, c. 1930 and lived in the area.
Re. Hiraeth's reference to G**gle translator: have seen some weird translations produced by that system.
Emyr