Is there any thunderbolt device which supports daisy chaining and costs less than £100?
I have recently run into a similar situation as yours. Both of the proposed solutions below do not use expensive gear like thunderbolt docks or monitors, and can achieve the same (or similar) desired end result.


This Thunderbolt-to-Dual-HDMI adapter allows your to connect two 1080p monitors to a single Thunderbolt port, and have both those monitors act independently from one another (ie. they are not mirrored). The adapter is also passive, which is nice.
Buy a Chromecast. This solution is sub-optimal, and is dependent on you having a decent internet connection, but with this $35 device, you can stream a browser tab, your desktop, audio, video, and more to an external monitor. The third monitor can then be added with a simple Thunderbolt-to-HDMI adapter.