Radiator TRV's

I've always understood that a Drayton TRV(4) should always go on the flow side of a radiator and the bleed valve goes on the top of the other end of the rad. Having moved onto a new, to us, old house a number of bleed valves are on the same end as the TRV. I therefore turned off the TRVs and waited for the system to cool and then turned them on one at a time and the majority that have the TRV & bleed valve on the same end heated the pipe from the lock shield valve before the TRV side, indicating (to me) that the TRV has been put on the wrong end of the radiator. 1). Am I right in my thinking that the flow side of a radiator will heat up before to return side? 2). If they are on the wrong end, is it simpler just to put another Drayton TRV (bi-directional) on the side that currently has a lock shield valve (I have spare TRVs), and then install the Hive TRV top on the flow end and a blanking cover of the other TRV, but if I do that do I have an issue trying to balance the system with TRVs on both ends, although only one end would have a Hive TRV top on it. 3). As balancing the system always seems a bit fraught, would I be better installing completely new Drayton TRV 4s on all the radiators as these now come as self balancing (but are not bi-directional). Apologies for all the questions.....