I’ve done plenty of Monday to Friday working away from home and have stayed in a variety of places. I get a weekly amount to pay for accomodation but always try and make a little. As mentioned before depending on where you are working Travelodges are a good option. I worked in Oldham for 12 months and there was three I moved between for the best rate. Used to book 6-8 weeks at a time and payed as low as £10 per night, the average probably was £19-£23 per night.
Last year was working in Holbeach Lincolnshire and stayed in a local pub, was basic but got an evening meal rather than breakfast and was only £25 per night. Local no frills pubs are always a good option too.
Final places were bed & breakfasts but these seem to be getting quite expensive now at £30 plus per night.