Boilermate II Descale .. help!

Have a BM II, 200 litre size, that deffo needs a descale. Well over 12 yrs since last one and I'm in a relatively hard water area.
Heats the water ok but the pressure from hot water taps is much lower than the cold taps.
I have contacted three local 'heating engineers' who say they can do a power flush on the system which (they say) will remove 'some' of the scale ... but I'm certain this will not have much benefit compared to a chemical descale.
I'm prepared to do the descale myself but will need a pump. I know I'll need to replace mixing valve prior to descaling.
Questions.
1. Anyone done a DIY descale ... what equipment did you need (hire?) and what chemical descaler. I've been told Fernox DS3 is ok to use.
or
2. Anyone know of a 'professional' descaler who covers the Newark area (Post code NG24)
Thanks, James

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Hi
On home page 2nd one on list are advertisers.
Thermal solutions may cover your area.
There may be some one else.
I descale BM's, and have a small descale pump for the job.
if using a power flushing pump there are 3 factors.
1; most will be too powerful.
2 you also need an adapted mixer valve for connecting the unit to the BM.
Gledhill charges approx £75 to £100 for these.
3 if using a powerflushing pump you will need more DS3 as being bigger unit the min level is sometimes 5 litres.
Norwich to Newark is at least a 200 mile round trip
So my charge would be £400 to £450.
If you could get a neighbour interested in a descale that would reduce the cost.
The above does not include a new mixer valve.
But I would advise a new one is fitted.
Mike