Littlefuse do several 5x20mm fuses with 250V 1500A interrupting protection.
You misspelled the brand name or bought some really, really wonky fuses.
Don't play with safety.
For use in multimeter to protect against accidentally applying current measurement to a voltage.
You need to pick a solution adequate for application.
Measurements in different environment require different protection measures, you know. If that is for laboratory environment, CAT I rated gear is adequate, 300V would do in your UK case. Here I would recommend IEC 60127-2/1 fuses. These are not rated for this exact voltage but as long as you stay below 1500A of prospective short-circuit current (PSCC), you should be safe.
Just be aware those fuses, reliable, cheap and available in most grocery stores, are designed for <250Vrms
and <1500A PSCC
and power factor of 0.7 to 0.8.
So no, you cannot charge 1F low ESR capacitor to 200V and get close to it with such meter because this energy is going to rupture the fuse, even without exceeding 1500A. The current during short-circuit has to ramp up slowly and be limited by reactance to give the link the time to interrupt the loop and pull down the arc well before current reaches 1500A. If you want to know more about "fuse abuse", ask mikeselectricstuff about
destructotron MCB. Same applies to playing with inductors, voltage must not raise too fast, and the energy dissipated has to be smaller than what it takes to melt quartz sand, before it evaporates, rupturing the housing.
If you exceed parameters of the fuse, it is going to split the housing and then it might ruin your day. There are fuses that do not come with this tight current and voltage ramp-up limitation and can work even with very high and very low cos(phi) but these are not general purpose fuses designed for short-circuit and overload protection. Might work or might not work - just are not designed for the job and not tested for this.
For CAT II or CAT III mains jobs - forget it. PSCC in my place is well over 2kA and I think UK single phase grid makes PSCC even higher than elsewhere.
Get a clamp meter - use adequate tool for current measurements in distribution boards.