It depends on the circumstances.

The train company for that route is East Midlands Railway, their delay claim page is here https://www.eastmidlandsrailway.co.uk/help-manage/manage/make-a-delay-repay-claim

The taxi is possibly an issue, normally train companies will put passengers in taxis where no other option is available, these taxis are paid directly by the train company.

If you have hired your own taxi then you will have to justify that decision as it is not the usual procedure for passengers to get unauthorised taxis.

If you were delayed by at least an hour, then you can claim compensation for delay here:

https://www.interrail.eu/en/support/delay-compensation

For all other claims, you need to contact the operator.

Delay Repay is based on the fare you paid, in this case zero! If you have the taxi receipt you may be lucky but rail companies are loathe to pay out on taxis they didn’t authorise. 

I don't think the pass was free of charge… as I wrote, Interrail is responsible to give any compensation for delay, which is indeed based on pass price.

Absolutely right, but it isn’t exactly a lot of money. If it is less than 4 euro it will not qualify. By my reckoning with a 7 day pass (335 euro  adult 2nd class) a delay of over 120 minutes would be worth about 15 euro. Delays over 60 mins would get a 7 euro rebate and under an hour would get nothing.

https://www.interrail.eu/content/dam/delay-compensation-documents/Compensation-amounts.pdf

Sorry I misread the link. Just to be clear the Delay Repay scheme in Britain would not cover this. They might consider an ex gratia payment though but it depends on the circumstances. I would love to know how you get on with a claim through Interail.

Don’t understand people asking all the time for refunds.. especially as it doesn’t really pay off doing all this stuff for getting a few euros… For the wasted time better to work and earn easier money that way :-D

I fully agree with you, delays may be annoying but  they are just a fact of interrailing and need managing. The best advice from this forum is simply make life awkward for the train operator when you finally get to your destination, and if necessary get them to fix it, as is their duty.

In the event you do not get satisfaction just get on with plan B,

Yes upon research the amount may seem insignificant, I was just wondering who would be best to contact. Inter rail or eastern railway as The taxi cost 100£, it was a cancelled train not delayed. Ive since done both thanks to the helpful links from the forum. 

That is simply not true.

All tickets are valid for delay repay, this includes day tickets, rover tickets and rail passes.