Ciao SieMad,
Did you find a solution for your wedding vows?
You didn't mention who you had contacted but since you mention travel expenses, I suppose it was someone outside of Siena.
If you want the blessing in English, I'd try with the two churches in Siena that offer english mass. I found on this page
http://www.comune.siena.it/Il-Turis...ligione/Luoghi-di-culto-e-cerimonie-religiose
that the Basilica of San Francesco offers english mass in summer, and the Basilica di Provenzano on holidays.... so that means they have the means to bring in someone to do the mass in english or even a priest within the diocese who speaks English.
If you're still looking, I would suggest you contact the two churches and see if you can get in touch with someone who can help you out from there. Unfortunately all I found were phone numbers and this is where a local event planner might help make the calls for you. I would suggest you contact Cindy if you still need help and see whether she might be able to make the calls for you and find a priest from Siena to do it for you, maybe in one of these two churches who already offer mass in english at one point or another during the year. Here's my interview with Cindy, with links to her site:
https://www.discovertuscany.com/weddings-in-tuscany/cindy-salgado-tuscany-wedding-experience.html
Luoghi di culto Basilica di San Francesco - Piazza San Francesco
Tel. - E-Mail - Sitoweb +39 0577289081
Orario Tutti i giorni: 7.30 - 12.00; 15.30 - 19.00
Celebrazioni Sabato e Vigilia delle Festività: ore 18.00
Domenica e Festività: ore 10.00; ore 11.15; ore 18.00
Celebraz. in lingua: in estate la domenica alle ore 9.00: SS. Messa in inglese
Luoghi di culto Basilica di Provenzano- Piazza Provenzano
Tel. - E-Mail - Sitoweb +39 0577285223
Orario Tutti i giorni: 8.30 - 12.00; 16.00 - 17.30. Lunedì pomeriggio chiuso.
Celebrazioni Sabato e Vigilia delle Festività: ore 11.00
Domenica e Festività: ore 11.00
Celebraz. in lingua: Pasqua e Natale: SS. Messa in inglese