had a local plumber round for a quote on a new boiler , my house is a large 4 bed detached with attic room as well with a rad . he told me to go with the viessman 35 kw 100 system series model as the 200 is being vaised out & the 100 has all the features of the 200 and has built in weather compensation , is this correct advice .he also said to use peglar TRVs as the drayton tvr4 has low water flow