Didn't get your message until just now but have made a bit of progress with trial and error over the last few days.
I changed the drop down manually so it carries over the price and size. I am pretty sure I already tried doing it so that it used recordset1 but that didn't work.
I now have the following for my dropdown:
<option value="<?php echo $row_options['OptionPriceIncrement']?> <?php echo $row_options['size']?>"<?php if (!(strcmp($row_options['OptionPriceIncrement'], $row_Recordset1['size']))) {echo "selected=\"selected\"";} ?>><?php echo $row_options['size']?> - £<?php echo $row_options['OptionPriceIncrement']?></option>
This seems to be working so far, but got to set up the checkout pages next. does the above look ok to you?