For teaching / learning it's hard to beat Quartus Prime Lite - the virtual JTAG infrastructure (for SignalTap logic analyzer) is much better than the other options. (It's easy to create custom virtual JTAG modules to control and read data from a running design, and these will happily coexist with the logic analyzer.)

Dev board wise QMTech on AliExpress have some really nice entry-level dev boards - the Cyclone 10CL025 board, the daughter board and a clone USB-Blaster cable for programming would weigh in at well under £100.

The Tang Nano 20k is a solid and affordable choice for a Gowin chip (though be aware that this particular chip's PLLs are a bit limited and its block RAMs don't have byte enables). The JTAG stuff works but isn't anywhere near as advanced as Intel's.

For Lattice ECP5 there are several options - and these chips are well-supported by yosys/nextpnr and oss-cad-suite in general.

I quite like the IceSugar-Pro ECP5-based board and associated breakout board - but it has a quirky built-in JTAG adapter which isn't supported by the Lattice toolchain, so you'll have to use OpenOCD or OpenFPGALoader to program it, and you can't use the vendor-supplied internal logic analyzer. Its FPGA is well supported by oss-cad-suite, though, which is a big plus.

IcePi-Zero is also well worth considering, available from CrowdSupply.

ULX3S is very nice, too - but as far as I can see it's only available for pre-order on the next production run.