There are some monthly contract-style mobile deals, where you only have to give 30 days notice, not tied in for 12 months.
Have not really looked at them as CarphoneWarehouse / e2save show deals from Vodafone, Virgin and TalkMobile where you can get hundreds of texts for small amounts (10, 15, 20 quid) on their PAYG deals.
Talk Mobile offers "unlimited" (but reading the small print and it's closer to about 100 texts per day) texts for periods of 7, 14 o 28 days depending on the top-up amount on simple PAYG SIM.
You can also opt to pay on one of these rolling contracts (presumably with a credit check?) - see the web page - ten quid a month give [300 minutes + 300 texts] or [100 minutes and unlimited texts]
Loads of possible combinations, probably to compete with the old T-Mobile mix and match style option. Only you know how many minutes and how many texts you might want so you can spend all afternoon looking at the 'view all tariffs' links for all networks on that web page and see if something takes your fancy!
As for landlines, the minimum now is usually 12 months with BT (and 125 installation). so you are looking at roughly 12 quid/month + install with BT (approx 275 even if you cancel after 4 months, plus phone calls, though you can use 1899.com for cheaper calls and get weekend calls included by BT). If the line is already there, you might get the installation fee waived if there is a dialtone, as BT would prefer to get a customer than lose them to (say) TalkTalk.
Some others offer free install but 2 year contract (eg Opal.co.uk, 13+VAT/month for line rental [min 2 years] and expect you to have broadband at 10+VAT for minimum of 1 year)... With Opal it would be (312 + 120) +VAT so much more despite the free line installation.