A lot depends on what you mean by mobile broadband, manu of these inclusive deals only allow you to view the webpages via the phone. If you want to connect via e.g. a laptop then these deals won't cover it. You wil need a specific data package to cover the use. Read the terms and conditions before you sign on the dotted line.
in my local 3 store they were offering a free phone, 500 mins unlimited texts, 12 month contract for £25 PPM 12months. But you could also get there mobile broadband dongle for £5PPM 1gb usage. so £30 PPM for a decent contract and mobile broadband
As an existing 3 customer I'm eligible to a 50% discount so I've taken the plunge and opted for the Broadband Plus for 18months (only wanted the 12 month, told that it was for new customers only) still a good deal at £7.50 a month and got the Huawei E169 thrown in for free.
Living in Portugal, I have a prepaid contract. Of the amount I pay in to my account at my own discretion (with a minimum of an accumulated total of 25 each 2 months), the operator deducts the calls cost and a fixed 7.50/month charge for broadband internet traffic up to 100Mb/month. Sms within the same operator network are free. The operator is TMN wich has by far the largest stake of the market, and my phone is N95 8GB.
Vodafone and Optimus wich are the other 2 operators have similar offers.