We've never had trouble renting, but maybe that's due to location. We've rented one place in Newcastle, and two places in Worcestershire. DH (UKC) moved to Germany right after university and lived there for 3 years before we met and then moved to the UK and tried renting. Any potential credit he had would've come from his student days 3 years before, when he didn't have many financial commitments and wasn't all that responsible with money. I'd also opened a student bank account in the UK years before but besides that had no credit.
At all three places we've only ever had to pay the standard 1 or 1.5 months rent as a deposit and then just paid rent monthly in advance. We'd actually moved to Newcastle for a job offer, so DH had been at his job less than a month when we started that lease. The other two leases we got when DH was self-employed and had really erratic income and I was only working part-time, but neither landlord seemed to mind.
I found the reference thing a bit strange. They did want a reference from our last landlord. Our second landlord was incredibly slow and would only reply to things by post, so instead of that reference our current landlord accepted a copy of our last tenancy agreement and 6 months worth of bank statements to prove that we paid our rent on time. The other references they all wanted were two character references for each of us. One of my character references was my mom's best friend in America who's known me almost my whole life, and the other was a British co-worker of my MIL who I'd met a few times in the UK.
If you do run into trouble with not having enough credit I agree with the idea of living in a houseshare until you find a place to rent. That way you'll have time to find a landlord who is okay with your circumstances (or if that's really difficult you can start building up your credit by maybe opening a bank account, starting a job, etc), and you'll also get to visit the places in person before deciding.
I don't think you'll have a problem with either opening a bank account or getting a mobile phone contract. From personal experience we haven't ever had problems with either of those. There are threads on here about opening bank accounts and which banks are more difficult than others, and if you are having trouble you can always open a low-risk account for the bank that doesn't have an overdraft or reserve. With mobile phones if you have trouble getting a contract there are also plenty of Pay as You Go (PAYG) deals where I don't think they'd care about your credit rating.