Ultra V1770 - my first telly and Im struggling

[Exiled Yorkshireman]

Turns out there were several problems, two of which have been resolved:

1. The 30L1 was bad, Replaced with  PCC84 brought a major instant improvement
   
2. The aerial socket/isolation capacitors were bad. The whole assembly had had a major bash, Fixing it has taken a whole day, partly because I couldn't totally dismantle it. Part of the metalwork is used to secure the mains dropper to which it is screwed via what I think is a large asbestos washer. I didn't want to disturb this.
   
3. The IF needs tuning. Many of the cores are rattling around as the thin strands of rubber previously securing them have perished/disappeared.
   

Question: what is the general consensus as to the best way of reversibly securing the cores?

I'll soon turn my attention to building a Hedghog L, then more tweaking and working on the cabinet....