Well, after looking around for weeks, I finally saw an article on Mashable about InvoiceBubble, from the developer of successful Project Bubble.
invoiceBubble is less than the price of a posh latte at just £3.50 / $5 per month.
Whilst mainly targeted at the US market, the developer Stu is based in England, they recently moved their servers to the Rackspace Cloud, so this should result in improved uptime and speed.
I decided to choose InvoiceBubble over FreeAgent due to my accountant not ‘happy’ to use its advanced feature set, so I felt it was unreasonable to pay considerably extra and not use many of the very good features.
InvoiceBubble makes Invoicing easy, with recurring invoices, PDF Invoices attached to emails, CSV exporting and customisation and part-payments on its way soon.