Diagram

Getting to grips trying to understand heating system in house after having warm air in old house for 18 years. After moving in had old boiler 30+ years serviced (Glo-worm space saver 50b mark 2) by corgi bloke recommended by colleague. Said boiler old but reliable..like me. Had new rad fitted, trv,s fitted on all but hall rad near to stat. System power flushed and balanced inhibiter added as it had been neglected buy prevous occupent. Nice and toasty. However heat stopped downstairs. Found advice and probable answer on this fab site ....Pump(grunfos 2 speed super 4) assume this is old too. Only works when on 2nd setting instead of 1st. Realize this is only short term answer. Tried explaining to hubby & tried to find amazing diagram that I came across yesterday...moving arrows...ect.LOST IT!!!!Please can someone direct me to it. Also any advice on possible replacement pump for 4 bed house with12 rads, 2 showers 1 bath and 5 sinks? Don't intend to replace boiler untill I have too. Sorry for waffle but I know you need as much info as possible to help.
THanx Reromac

Pump running on 2 is fine could get away with 3 .

As for the site with diagrams click your history button on tool bar.

Only 1 or 2 no number3. But thanx. No luck with history either as following lots of links at base of page about all different prob.Diagram from regular contributer and had lots of praise so someone out there must recall it