Ask HN: Accounting solution for B2B SaaS business

I've built up a reasonably successful business selling services to SME's in Europe. We are using Xero to do our books, and have written (way too much) plumbing between Stripe, GoCardless and Xero to try and automate the invoicing/billing/accounting process as much as reasonably possible.

The problem is that Xero has a "soft limit" of 1,000 transactions per month, and we are way past that limit already. We are about to spin off a new company that (we hope!) will outgrow Xero.

Is there a 'best of breed' accounting system similar to Xero that will scale with our needs:

- Must be able to deal with international customers, FX, tax rates etc - B2B, so all our customers will expect to receive invoices, particularly for tax - Scale to 100k transactions per month - Reporting would be nice - Compliant with UK rules for our end of year accounts