Don't like Ursula Ivy at all, at all.

Ursula Constance is much better. Constance is lovely

ursula Rose

Constance.

I would either go with a one syllable or a 3 syllable name - sounds more musical. I would also avoid anything ending in a 'ah' sound as I know an Ursula Eleanor and think it sounds horrid!

dah-dah-dah DUM eg. Ursula Jane
dah-dah-dah dah-dah-dah eg. Ursula Harriet

Of those two though I prefer Constance because the C give a good break between the two names.

My friend has an Ursula Veronica

Out of those, Constance. For my suggestion, I like Jean as a middle name, it just sounds nice.

I like Ursula Ivy, too.

Mae and Rose just sound like obligatory add-ons.

Ooh, Ursula is top of my shortlist! (Unfortunately having trouble persuading dh of its merits...)
Of your 2 options I much prefer the combination Ursula Constance (Constance being top of dh's shortlist!), although I do love the name Ivy.
Other ones on my list are:
Ursula Beatrix
Ursula Mabel
Ursula Joy

So lovely to see someone using Ursula!

I like Ursula Ivy. It's very spunky

I see what you mean but personally don't think it merges as much as some names and with a name ending in 'a', you'd have to avoid any middle names beginning with vowels to avoid merging completely....