You mention TfW 67's, are you planning the Cardiff or Manchester one?
It would be the manchester one - I've just worked out that I can do the evening trip to Llandudno and get back to Stourbridge for a B&B and then the first Chiltern in the Morning...
New Plan as follows:
Thursday - Cardiff - Penzance ( GWR HSTs ).
Thursday Night - Sleeper to London
Friday - Midland Main Line HSTs
Friday Night - Sleeper to Fort William
Saturday - Mallaig to Skye to Kyle of Lochalsh to Inverness
Saturday Night - B&B Inverness or Glasgow
Sunday - Trip down West of Scotland
Sunday Night - B&B Edinburgh
Monday - Scotrail HSTs and XC to York
Monday Night - York for B&B
Tuesday - TPE for TfW Llandudno
Tuesday Night - B&B Stourbridge
Wednesday - Chilterns & XC to Cornwall for HSTs back to Cardiff