Localizations for UK and Spain AR invoice output

Summary

Spain and UK require specific content to print on the invoices. How can this be achieved with localizations (or other)?

Content

Specifically, in the UK, it is required to print the VAT amount in GBP equivalent when an invoice is in non GBP currency. Is there a localization for this, or is the only option to build custom logic in the report?

Similarly, in Spain, it is required to print a unique and sequential "ES" number on each invoice to be VAT compliant. 

Any ideas/experience on these?

Version

19D