Calling on the knowledge of any plumbers out there.

I am about to have an extension done and am looking for some guidance on
whether my current boiler will be able to cope with the extra
additions. I appreciate people may not be able to give me a definitive
answer but something along the lines of
a) definitely need bigger boiler
b) may be sufficient but need plumber to do calculations and confirm
c) should be ok
d) more than enough

The current setup is;
3 bed semi, boiler is vaillant model no. vcw gb 242 eh, nominal input
101030 BTU(28.8KW), nominal output 81900 BTU (24KW), burner press mbar
5.1

Front room 15ft by 11.9ft with standard double panel radiator
Lounge 20.5ft by 11.8ft with standard double panel radiator and patio
door to garden
kitchen 15.5ft by 7.5ft no radiator
Bedroom 1 & 2 12ft by 11ft with standard double panel radiators, Bed 3
8ft by 7ft with standard double panel radiator
bathroom 6.5ft by 6.5ft with standard single panel radiator
entrance hallway with standard double panel radiator

After extension, in addition to the above there will be
new downstairs toilet and basin
radiator in kitchen (15ft by 13ft) (approx 6000 BTU)
radiator in study (10ft by 5.8ft) downstairs (approx 2000BTU)
radiators in bedroom 4 and 5 (10ft by 5.8ft & 15ft by 5.8ft) (approx
1400BTU & 2000 BTU)
ensuite shower room (6ft by 6ft) with radiator (approx 1400BTU), shower
may be electric, not decided
larger bedroom 2 (extended by further 9ft by 8 ft)

Any comments/advice appreciated

Thanks
BS