I still call bullsh*t!

First, if one looks at the specs of all of Scott's current lineup of 710 bikes they are all spec'ed with the same shimano XT M8000 double crankset and pressfit BB with the exception of the Contessa 710 which comes with M622 crankset (deore level) and the Gambler 710 which comes with Saint crankset.

The entire XT M8000 groupset can be purchase for £430 and the M8000 crankset cost only £109. The average price for the pressfit bearings/cups is only around £22.

If the OP has the Contessa 710 then replacement parts of the same spec as the original are even less expensive than the other 710 models. The M622 crankset sells for between £60 and £79 and the bottom bracket is roughly the same price as that used on the other 710 models.

Second, the shop replaced the OP's BB at cost of £350...the BB axle is part of the crankset. So if they replaced the BB bearings, cups, and Crankset then they totally ripped the OP off because those parts should not have cost much more than the £109 for the crank, and £22 for the bearings/cups....it should actually have been less because the crank is available without the chainrings and the shop could have move the chainrings to the new crank if they actually replaced it. If they only replaced the bearings/cups then they totally took the OP for a ride.

Third, a few months later the shop replaced the bearings/cups at a cost of £100 for a part that costs on average £22.

Even with the cost of labor added in to do the work they have seriously ripped the OP off.

No matter how you slice or dice this, the the OP has been getting F***ed by this shop...especially if this is something that should have been covered under warranty. And this is especially true if one looks at the 2014 model year specs (since the OP indicated their bike is 20 months old) which indicate the XT M785 crankset which can be purchased for roughly £92.

OP...find another shop, your current one is totally screwing you over.

-j