c/heating header tank

[greengrass]

Myson Marathon 80c floor mounted boiler:
To avoid a further stitch up price which a widowed friend of the family recently suffered £840 for 8 bog standard rad valves.
Problem: c/heating tank over flow pushes out water intermintent when boiler on.
the water inlet to the tank is ok it shuts of 2" below overflow. There is a hook shaped pipe about 1" dia over the tank could this be expelling water every so often. I think it's what's termed a 'Vent" pipe looking at central heating diagrams. What would the cause be and what is the solution and rough £'s cost many thanks.

[greengrass]

[quote="greengrass"]Myson Marathon 80c floor mounted boiler:
To avoid a further stitch up price which a widowed friend of the family recently suffered £[color=#FF0040]840 [/color]for 8 bog standard rad valves.
Problem: c/heating tank over flow pushes out water intermintent when boiler on.
the water inlet to the tank is ok it shuts of 2" below overflow. There is a hook shaped pipe about 1" dia over the tank could this be expelling water every so often. I think it's what's termed a 'Vent" pipe looking at central heating diagrams. What would the cause be and what is the solution and rough £'s cost many thanks.[/quote]

I'm begining to wonder about the £840 so have decided to break it down.
Cost £840. Work time 7.5hrs incl travel. 8 standard manual valves retail £29.52 give 10% off trade = £26.57+£25 for vehicle etc £52 (rounded up) £788 / 7.5hrs = per hour £105 labour charge and he took away the detailed receipt after distracting actions, which proved he doesn't want others to see the stitch up he's pulled.