Manufacturing firm British Polythene Industries (BPI) said its full year results would come in at the top end of expectations.It said structural changes it recently made in the UK, as well as a strong performance from its European business allowed it to overcome a difficult trading environment.It has also seen raw material costs slowly fall, which it put down to poor demand and an increase in the volumes of imported polymer from new sources in the Middle East.However, the firm was also keen to manage expectations, saying there was subdued demand from many industrial customers and, at best, overall flat volumes from the retail sector. It currently expects total volumes for 2011 to be slightly below 2010. The company's shares rose 3% following the announcement.In August BPI announced pre-tax profits for the first six months were up £2m to £15.1m, with profit after tax up from £10.2m to £11.4m. Borrowings also improved, dropping from £49.5m to £38.5m.