> More recently, nearly all flash drives have been formatted FAT32 or NTFS, either of which allows much larger single files; but you still may hit a file size limit less than the full drive size.

Actually, there is no NTFS file size limit, but there is a limit of 4GB on FAT32 - depending on bit rate, that is about 2hrs worth of SD Freesat video. As many flash drives are formatted FAT32 by default, this is probably the problem that the OP Chris is up against.

Suggest reading the TV manual very thoroughly, or asking a question through the manufacturer's website, to determine what drive formats the TV understands. Likely ones other than FAT32 are, as already mentioned, NTFS (the default format for all Windows Operating Systems, OSs, since W2k/NT), and ext3, possibly ext4, which is understood by Linux. The main reason that the latter is popular despite the relative lack of end-user PCs is that, being and open source OS, it is used for preference for many bespoke boxes such as routers, set-top boxes aka STBs, and TVs.

If, as is likely, Chris has a Windows PC and the TV will understand NTFS, then (s)he could try reformatting it in the PC as NTFS. Be aware, however, that sometimes attempting to do this can actually 'break' the stick, because at the lowest level not all of them behave exactly like a conventional rotating hard disk. ISTR that such 'broken' sticks can be be repaired by special software, but I have no personal experience of this.