Hello Ian,
Thanks for your reply, I have played around with it and went through the docs a few more times but I still have some issues where you maybe can shine a light on

As of 2.4, BASS_WMA_StreamCreateFile shouldn't actually prebuffer at all by default (BASS_CONFIG_WMA_PREBUF can be used to change that). Also, BASS_ChannelPlay shouldn't be held-up by prebuffering either. Instead, playback will start stalled and be resumed once prebuffering is complete.
If you want to monitor the prebuffering progress, you can do so using BASS_StreamGetFilePosition (BASS_FILEPOS_WMA_BUFFER).
I tried to use the same routine as I would monitor a 'normal' streams progress:
Channel := BASS_WMA_StreamCreateFile(False, PChar(URL), 0, 0, BASS_STREAM_DECODE);
repeat
Len := BASS_StreamGetFilePosition (Channel , BASS_FILEPOS_WMA_BUFFER);
if (Len = DW_Error) then
Break;
Progress := (BASS_StreamGetFilePosition(Channel , BASS_FILEPOS_DOWNLOAD) -
BASS_StreamGetFilePosition(Channel , BASS_FILEPOS_CURRENT))
* 100 div len;
SendMessage(win, WM_UPDATE_STATUS, DWORD(Ch), DWORD(PChar(Format('Buffering %d%%',[Progress]))));
until
Progress > 75;
edit: But now I read the manual again, and I came with this, seems to work

(it does not update very fast thoe)
Len := BASS_StreamGetFilePosition (Channel[Ch].Mp3, BASS_FILEPOS_WMA_BUFFER);
if (Len = DW_Error) then
Break;
Progress := Len;
SendMessage(win, WM_UPDATE_STATUS, DWORD(Ch), DWORD(PChar(Format('Buffering %d%%',[Len]))));
BASS_TAG_WMA_META gives the most recent mid-stream tag (script) to be received in the WMA stream. Most WMA streams do not include any, but the WMALIVE example does (the "Caption" box), so you could use that to test things.
Same here, tried with the wmalive example, the Title box is read out fine, with BASS_TAG_WMA, but if I want to read out the Captaion, and use BASS_TAG_WMA_META, I get nil

To read out all the lines I tried:
Meta := BASS_ChannelGetTags(Channel, BASS_TAG_WMA_META);
ShowMessage(Meta);
if Meta <> nil then
begin
while Meta^ <> #0 do
begin
ShowMessage(Meta);
Meta := Meta + Length(Meta) + 1;
end;
end;
But no luck...
That ASX file appears to contain only 1 stream at this time, and it's playing fine here

Perhaps it was a temporary server problem that you experienced?
Hm true, I swear it was six before

But still, if I want to load this ASX directly in bass it will give me the error BASS_ERROR_FILEFORM.
It works at yours?