There's no word that they attended or not, so we won't know for sure.In Ballad for Wind Instruments and Canoe (S02 E06), Cyril says to Arnpepper:
"I can sympathize. I can understand the feeling of talent unrecognized, superiority unrewarded."
Blamire, despite his military experience and his artistic interests and ambitions, is back in Yorkshire, used up, unwanted, and up to this point without romantic prospects, is a man filled with regret, and it's all stated in his remark in this episode. No wonder Cyril picks up and leaves the instant he has the opportunity for marriage. Roy Clarke's writing out Cyril works for the character and its not just a neat-and-tidy instance of convenient TV writing. Blamire, as far as we know, gets a "happy ending", but did he invite Clegg and Compo to the wedding?