Paddington?
TM is a Guard, just as a Conductor is, but TM is on the 'High Speed' side (HSTs and 180s), while Conductor is 'West' (Sprinters). At some depots where both operate, there is potential to sign everything as a 'cross traction' TM. The recruitment is the same, candidates can potentially apply for either/both and be offered the other position instead. Best of luck!
There are LTV (London Thames Valley) Conductors too, at Reading and Redhill, for Turbo and 150 work on the North Downs, Basingstoke and Marlow branch, and as BestWestern says Reading TMs are cross traction and do the aforesaid Turbo work and HSTs/180s on the Cotswold Line.
The tests for both roles are the same:
Safe Concentration and Attention Test (SCAAT) - similar to Group Bourdon
Rules Acquisition Aptitude Test - comprehension of written passages
Ticket Selling and Checking Test - basic mathematics around ticket sales
After completing these there is a final interview, consisting of:
Flipchart Exercise
Group Discussion Exercise
Interview with Crew Manager
If you need any more help, do let me know.