We had lodgers for a few years in London when my older kids went to university. I did it through an agency run by one of the mums from our primary school, which reduced the risk of problems, although she took a cut of the rent in return, so swings and roundabouts.
Her speciality was finding short-term accommodation for young interns, mainly from Germany. It worked well, and we had very few probs.
I would say think long and carefully about the layout of your house and your family's living patterns, so you can anticipate what will annoy you and put boundaries in place from the off. Especially if you have a kitchen diner you will want to give some thought to when the lodger can use the kitchen so they're not impinging on your cooking space or family time. What kind of cooking are you prepared for them to do? Heating up ready meals in the microwave or making sarnies is one thing, cooking full-on elaborate dinners is quite another. Ditto bathrooms if you don't have an additional bathroom for their exclusive use - we only had one family bathroom, so we had to tell lodgers that they would need to do leisurely bath or shower sessions in the evenings, and morning bathroom visits needed to be brief, otherwise we'd not have been able to get ready ourselves. Where and when will they do their laundry, and how will they get it dry?
Think very hard indeed about whether they can have friends staying over - we were relaxed at the start, but later moved to a hard no, as you've then got multiple people clattering around, using the bathroom/hot water supply and generally making your family house feel like a student let.
There are agencies that specialise in Monday-Friday lets, and if I were doing it again I would probably start with that, as the chance of conflict is reduced if they're not around over the weekend.