In case anyone's still looking for an online Welsh/English translator, I can recommend this:

Online Dictionary / Geiriadur ar-Lein

and especially this:

English/Welsh Meta-Dictionary

What's a meta-dictionary and why might you want one? The introduction describes it as:

an alphabetical listing of all the things you might want to try if you fail to find an item in a Welsh-English dictionary. For example, say you happened upon the word "trewaist" in your reading. You could look in an ordinary dictionary and find that "trew" means "sneeze", but it's a noun rather than a verb. You might be tempted to postulate that there is a verb "trewi*" for which the word you are seeking is a conjugated form, but you'd be wrong. If you look in the meta-dictionary under "trew-", you find that it is the stem for the verb "taro" before certain endings. You can also look up "-aist" to find that it is the ending for the 2.s. past ind. Putting it together you find that "trewaist" means "thou smotest", or in modern English, "you struck".

I learned Welsh at school for a few years, but went back to England before we'd got as far as conjugating a verb. The Welsh I learned - which I imagine was based on contemporary spoken South Walian Welsh - was more on the level of
Ydych chi'n hoffi te, Gwen?
Nac ydw, Gwyn, rydw i'n hoffi coffi.*
than anything involving the words "thou smotest". Meanwhile of course** we were singing lots of songs and hymns written in grammatical Welsh, none of which us English-speakers could make head or tail of. (I remember trying to work out "Calon lân" with a dictionary; I got stuck on "wy'n".) So I really like the meta-dictionary - it's basically the bits of Welsh I wasn't taught, all in one place.

*Footnote For The English: "Do you like tea, Gwen? No, Gwyn, I like coffee".
**Footnote For The English: it really was "of course".