My only concern about the trainline is the fact they charge an admin charge from any refunds for delays encountered.
No they don't. Delay Repay compensation is paid by the train operating company responsible for the delay. With no fees.
Trainline like most ticket sellers will charge a fee if a refund is requested for an unused (not Advance Purchase) ticket where no cancellations or delays are involved. They have a sliding scale based on purchase price. From £0-£5. Most
TOCs▸ charge a flat fee of £5 so if your ticket is less than the admin fee you get nowt back if you decide not to travel.