I have a 3 bed detached with 30yr old CH/HW system and have just got a
price from a local Corgi plumber for a complete new system.

8 rads, 4 with trv's, dual prog timer/roomstat, new gas supply from
garage to porch where I want the boiler and the quote price is £2800
with a Baxi Main 30 HE or £3000 with a Greenstar 28i Junior. This
includes removal of all old pipework, rads, tanks etc.

My Question is which boiler should I go for? No baths taken in this
house, just showers

The Baxi spec seems to show 2 heat exchangers (1 caste iron the other
alloy), the 28i only one? Hot water throughput on the baxi is more 12.1
ltr/min against 11.4 ltr/min Baxi states independent control of hot
water /heating temp, dont know on 28i Baxi is 11.9 to 31kw output,
Junior is 7.2 to 28kw

Any installers help point me in the right direction please