The only way of installing a Type A, B or F RCD in one CU, is having a split load board i.e having 2 busbars or cutting the exising one in half and prividing a gap between them, so they are seperated. However by doing so, you will typcally double the space required for the SPD’s alone as 2 will be needed if your going to installing them on the PV side, so in most cases a new split load board will be required to accomondate the number of useable ways.
By rights, if you have for example have a MK CU, you should use MK RCD’s, MCB’s etc, as they are type approved (type tested) to be used in the CU housing, this however, is not always followed and there are many other manufacturers RCD’s MCB’s etc that will be cross compatible.
Type F RCD’s are among the most expensive and depending on brand can be considerably more expensive than say Type B or Type A RCD’s, so potentially it cold be far cheaper to by a new CU by Fusebox or WCED, which are cheaper to beging with and still approved for use and with a Type A RCD installed, so you only have to buy one for the HP. However, not knowing the design characteristics of you HP, I can’t say for sure whether you should opt for Type B or F RCD*, if you remain uncertain to the system characteristics ring manufacturer helpline for advice. Note heatpump Type B RCD’s have different characteristics than your bog standard typical Type B AC RCD and are more expensive than Type F’s.
If it helps you can get single pole RCBO’s where the RCD and MCB are combined along single pole SPD’s but still need MCB for SPD – possibly freeing up valuable space.