Paul.

Just because the groom and probably the best man and perhaps the ushers too may be wearing morning suits, the guests may not be. So it is a judgement call for you. As I understand it and I may have misunderstood, you are attending this wedding as a guest. Might I suggest you try a modest amount of scouting to find out what the GUESTS are wearing. If they are wearing lounge suits, for example, it may pay you to tone down your attire a wee tad. A tweed argyll would be perfect in this case. OK I know you don't have one! But you would not want to be the only guest in a morning suit would you? If guests are wearing morning suits too, then get stuck in, with all the gear!