Hey, try this, I added this to the last image: style="width: 1px; height: 1px;"
<form target="paypal" action="https://www.paypal.com/cgi-bin/webscr" method="post">
<input type="hidden" name="cmd" value="_s-xclick">
<input type="hidden" name="hosted_button_id" value="SN3EQ3BCR7AMG">
<table>
<tr><td><input type="hidden" name="on0" value="Magazine">Magazine</td></tr><tr><td><select name="os0">
<option value="UK">UK £6.00 GBP</option>
<option value="Overseas">Overseas £7.00 GBP</option>
</select> </td></tr>
</table>
<input type="hidden" name="currency_code" value="GBP">
<input type="image" src="https://www.paypalobjects.com/en_GB/i/btn/btn_cart_LG.gif" border="0" name="submit" alt="PayPal – The safer, easier way to pay online.">
<img style="width: 1px; height: 1px;" alt="" border="0" src="https://www.paypalobjects.com/en_GB/i/scr/pixel.gif" width="1" height="1">
</form>
