I'm afraid I only had limited success at Kew last week. As I'd already started to suspect, MGB 17 didn't appear in the Coastal Forces reports for D-Day. However, I think I may have identified the set that it may fall within, although I didn't have time to begin going through them (there would appear to be a lot).
However, I did have a look in the Red Lists for May and June 1944. MGB 17's listed from 7 May to 11 June as being one of 4 MGBs operating out of Portland allocated to Force G. 97 refers to the Accounting station, in this case, HMS Attack.
She does not appear on the 18th June edition. The remaining 3 boats do, and are still listed as being attached to Force G. Interestingly the 18th June also marks the creation of a despatch boat flotilla at Portland. It consists of MGBs 7, 8, 13 and 21, but they are listed separately to the three surviving MGBs allocated to Force G. They had in fact all been part of an engine room training flotilla previously.
The index gives MGB 17 the following details: a W3, Y1. These detail equipment fittings in the boat translate to:
a = partially fitted with Asdic.
W3 = Fitted with radar (WC) Types 286M, 286P, 286PU, 286PW, 286. (286PU was the standard version of 286 radar in Coastal Forces, so it was probably this type installed).
Y1 = Interrogator, Type 241, fitted to WA set. (I'm not an expert on this stuff, but I think it has to do with Identification Friend or Foe (IFF) equipment).
Next time I'm back there I'll see what else I turn up.