Been using Protx/SagePay for the last 5 years and wouldn't look anywhere else - Only had to contact them a couple of times and that was when originally setting the account up.
Great systems, great API.
SagePay also offer a virtual terminal (included in the £20/month) which allows you to process telephone payments. You would however need two merchant accounts - One for "Online" and one for "Offline", but these would be placed under one overall merchant account with your choosen bank and if they charge a minimum amount per month you should only pay it if the combined transactional cut was less than the minimum amount, i.e. say your bank charges a minimum of £25/month and you process £x worth of transactions online which translates to £20 (their cut) and you process £x worth of transactions offline which translates to £6 (their cut), you shouldn't be charged the minimum fee of £25, as the two accounts combined did £26...