Hot on the heels of its newly-announced iPhone tariffs, O2 has revealed a series of attractive "bolt-on" packages that can improve the offering to customers.

O2's bolt-ons let users add extra calls and texts to their existing tariffs, and also include a range of deals designed to cut the cost of calling when an iPhone user travels abroad.

Separate £7.50/month deals promise users unlimited O2 to O2 calls, unlimited texts, unlimited weekend calls, unlimited fixed line calls or an extra 200 anytime minutes.

The company is also offering users the chance to sign up for discount country calls, offering cheaper calls from the following country blocs for £3 per month: USA and Canada; Australia or New Zealand; South Africa, Turkey, India, Pakistan or Bangladesh; China.

Finally, O2 is also offering discounts on calls made and received in Europe. "When traveling in Europe or Spain, receive calls for free and make calls to the UK and other included European countries for 25p/min." This costs £10 per month, or £5 to choose the discount in Spain. The deal can be tied for one month.

More information on 02 bolt-ons for iPhone users is available here.