By City AM reporter Next could upgrade its forecast for full-year sales next week as the retailer looks to capitalise on new business overseas. The clothing retailer reports its interim results on Thursday amid a backdrop of 28 per cent growth in its share price so far this year. Next reported a 4.4 per cent rise in sales in the first weeks of August, but has left its guidance unchanged for the rest of the year so far. Deutsche Bank analysts wrote that the six weeks of trading since then may make the company “more confident to upgrade the 2.5 per cent brand sales guidance for the second half”….