Yes, i have had it working, and it will probably work again temporarily the way things are going, like you say there must be a blockage or it needs a presure recharge or whatever the correct term may be, and yes a service/check in one hand and a repair in the other i know i know.
CHEERS...
I have a Sime Friendly format 80E and am having a wee problem with it.
When the boilder is required to produce hot water for central heating/ hot water taps it clicks on, and starts as normal, but within a few second the pressure rises and the boiler cutsoff i assume a safty mechanism...