I can say, without fear of contradiction, that it is MoD POLICY that Service personnel are expected to buy certain kit. I have on more than one occasion asked why the Customer was making no financial provision for fundamental kit. The answer (from serving officers) was, they have to buy it themselves. It's why Silvermans in Warminster do a roaring trade.
I know of one example where very expensive comms, which clearly hadn't been specified or tested properly, only worked in theatre because a soldier bought the correct ancillaries from a boot sale. Over £1k I recall. (I understand mess funds covered it). I watched him set it up and it worked a treat, but of course this is only a rumour forum and MoD would deny it.
Disgraceful abrogation of responsibility and duty of care.