If you're in the UK I would recommend the following:
- Barclaycard for your merchant bank account
- SagePay for the payment gateway
And if you're implementing recurring payments then I'd recommend Recurly.
After much trial and error this is the best combo that I could find.
If you're after something even simpler, try using hosted payment page solution from SagePay.
Make sure you take into account VAT when taking payments in the UK.