During the last show Graham did announce that £413,000 had been raised for the BBC Performing Arts Fund. At 14p per call that means 2,950,000 telephone votes were made during the whole series.
That didn't seem like very much to me, so I tried to find the same information for HDYSAPLM. ADWD and IDA.
The BBC Performing Arts Fund received -
£506,720 from IDA (£631,603 in total from the BBC) - 14p per vote means 7,094,080 votes for the whole series.
£364,776 from ADWD - (£453,383 in total from the BBC), but money from ADWD also went to Children In Need. The 12p per vote was split equally, so 6p per vote means 6,079 600 votes for the whole series.
£416,055 from the BBC in 2006/2007, but I can't tell how much of that came from HDYSAPLM. It was 12p per vote from this show, so if all £416,055 came from HDSAPLM then 3,467,125 votes were cast for the whole series.
So it looks like far less people voted for Dorothy than for Maria, Joseph and Nancy.