I've stuck with Ebico
http://www.ebico.org.uk/ since my first switch away from the 'usual' about 5 years ago. At the time, it was a very good deal. These days not so clear cut, but I like their model with zero standing charge, and a single unit cost (no 'this much more for your first so-many units'). I pay quarterly direct debit (i.e. the actual bill amount), and I think I'm getting a direct debit discount even though the Ebico tariff isn't supposed to offer this (the basis is 'same rate for all' no matter how you pay, including pre-payment mater). Looking at their rate table, it's presently around 14.5p to 15.5p per kWh depending where you live (Economy 7 available as well - I'm on that). I don't use much electricity (just the greenhouse that 'wastes' some!), so doubt I could save much by messing about switching again. With Ebico, you actually deal with SSE (who do the account admin for them), so to all intents and purposes, you are an SSE (Southern Electric) customer, but on a tariff that SSE probably won't switch you to without you applying to Ebico.
As you say, the smaller your usage, the more this true zero-standing charge model is a benefit - I used it to great advantage on an unoccupied house for a while!