Investigating adding SMS add on to Zoho CRM - Which is the best?

Investigating adding SMS add on to Zoho CRM - Which is the best?

We have a database of around 8000 potential clients who have form filled to give us data.  We need to reestablish contact with a large proportion of these and an SMS campaign is what we have decided upon.  Support have given me a number of potential integrations listed here:

BulkSMS, Clickatell, MessageBird, MessageMedia, MiSMS, Vonage, MSG91, BurstSMS, SMS-Magic, Twilio, Kaleyra, Elitbuzz, and Rakuten.

As a non techie, I could use some advice on which are/is the best and most simple to integrate please.

Thanks

Simon - Based in the UK and only sending within UK