Will these be ok for a road bike?
If you want even thicker larger tyres or some road tyres for a 29" mountain bike, Planet X has these Schwalbe's (700x50) for £7.99 https://www.planetx.co.uk/i/q/TYSCCEN/schwalbe-century-wired-tyre However there is postage on top so it only makes sense if you are buying other items really. They do a lot of great prices but like Halfords their prices are like a roller coaster. What is £5 one week can be £7.99 the next week and vice versa.
These are 700c tyres so it has to be the same size wheel. Then you have rim width compatibility which can mean small width rims can't take these larger profile tires. The chart I linked to gives a good guide to compatibility. Also these tyres would be suitable for 29" wheels I'm sure as 700c and 29" are the same wheel size with just rim width size varying. So someone with a 29" wheel mountain bike should be able to use these tyres depending on rim size if they wanted some more road suitable tyres. Also Germans call these 28" tyres I think but the important bit is 622mm iso. If you need 26" tyres there are always offers about just keep looking. 26" inner tubes are available from poundland and there was a recent offer on here for as low as £3 for 26" tyres.
700c equivalent is 29inch
So they won' fit a 26" mtb rim?