PIP very late appeal

Hi, Well I applied for PIP when I thought appropriate, being on Universal Credit already at the time, and never having had any esa -related issues before. My pip assessment was dismal, a mental health nurse who had no knowledge of orthopaedics. She required no load bearing for my neglected Achilles tendon rupture assessment.
Anyway, I requested a mandatory whatsit with same 2points result. I then received my two copies of decision letter and there was no, absolutely no mention of a time limit on appeals. So I kind of put it on back burner as many other issues were more urgent eg rent arrears due to benefit cap etc. Then when I come to appeal, I find it says 1 month time limit! I also find that my friends letter following mandatory whatsit does mention 1 month time limit, is this fair play or even admissible, and is it grounds for a late appeal?

Thanks Gordon, it was about 3 months ago, so I shall appeal as suggested.

A second issue is causing me great confusion. I have been on UC since Feb 2014. I became ill with severe undiagnosed myxoedema during summer 14, and since have alternated between being completely debilitated some of the time, and being able to work for say 10-20 hours only at other times, due to exhaustion, impaired mobility (misdiagnosed neglected Achilles tendon rupture) and pain. I have always tried to work when I can, but have handed in consecutive sicknotes ever since Nov 2015, mostly saying I couldn't work at all, but sometimes saying I could work a little bit. I deliberately asked my doctor to say I could work a bit, even though he said I shouldn't, because I was on the benefit cap with four kids and high rent. I needed to drag myself to work whenever feasible, though my earnings were paltry(on various zero hours contracts). I asked for the UC version of ESA to be applied repeatedly, on account of my sicknotes. I am now booked for a leg reconstruction operation later this month, and I rang up again, because the consultatnt said no way could I work at all for 4 months. I was surprised to hear that I got no sickness component because I did one hour or more work in each month of the last yaer. This contrasts with what my research tells me about people on esa being able to earn up to £110 per month for a year (WRAG). They told me no work at all is allowed on UC. How terrible is that?

thanks Gordon