Expensive? Not so much. There is a Onkyo AVR in MM just now for £20. That would do the job you are looking for. And 2 stereo and one centre Cambridge Audio speakers too, coming in at £115 for the 3. So £135 all in for a much nicer sounding set-up than all but the most expensive soundbars, I would wager.
Can't help you with space though. What is your TV sitting on? If it's wall mounted, what are your sources sitting on? Most stands for such equipment can take an AVR with ease. Wall mount the stereo speakers? The person selling the speakers is also selling stands for them for £20, you could always try and negotiate them into the deal for the 3 speakers. Keep the grill on the centre to help prevent curious fingers. I have a 3 & 5 year old. Curious as George. And they have never poked out my tweeters yet. But I do keep my grills on the speakers.