Interrail has a sale on currently for their passes, until 1000 CEST on 1 October.
They have 15% off passes valid for under a month, and 50% off 1 to 3 month passes- that means a monthly is generally cheaper than a 2 week pass (a hark back to the original roots of Interrail, as a student grand tour of Europe).
Reductions are automatically applied-no need for a code.
Once purchased they will be valid for 11 months. With the price being so much lower anyway than the former Eurail now may be the time to buy for a good value 2027 deal.
For Senior Passes (over 60) 1 month 1st class is £353, 2 months £419 and 3 months £485. The senior 2nd class is £272/£323/£374 respectively, so 1st class is excellent value.