AVERAGEIF / SUMIF with multiple ranges

Hi there. I realise this topic has been brought up before but the solution and question was slightly different from the problem im having.

I need a formula to average out various 'non-error' cells dotted around my worksheet.

My data is appearing in cells G8 G57 G106 G155 G204 & G253
The cells either have values of between 1and10, or -more commonly- have #N/A values. (purposefully used to avoid graph interpolation issues)

Is there any way I can do use an AVERAGEIF formula or some equivalent thereof to get the average of just the values that appear between 1 and 10 (i.e. ignore N/A values)?
Something like:
=AVERAGEIF((G8,G57,G106,G155,G204,G253), "<> NA()", (G8,G57,G106,G155,G204,G253))

I tried to get around the problem using a normal average, but the problem is persisting:

=AVERAGE(IF(ISERROR(G8), "", G8), IF(ISERROR(G57), "", G57), IF(ISERROR(G106), "", G106),IF(ISERROR(G155), "", G155), IF(ISERROR(G204), "", G204), IF(ISERROR(G253), "", G253))

Any help is appreciated.