can we combine HSRP and BGP?

HSRP is first hop redundancy. usually this applies to core Multilayer switches/ Rotuers. So look at it this way, from your Access Layer towards Core Layer, this is where HSRP is applied. You may also see first hop redundancy as Layer2 devices towards Layer3 device.

OSPF and BGP on the other hand are routing protocols. This is usually applied in between layer3 devices. The difference being that, OSPF is mainly used for your internal Layer network, while BGP primarily is used when interfacing you network towards the internet. NOTE: Interfacing to the internet doesn't necessarily mean you need BGP, in most cases where you only have one default gateway, or just on ISP, BGP is not advisable to be used. Usually a default route would suffice. Other scenarios when use of BGP is applicable is when:
1. You connect to 2 different ISP.
2. You have redundant connections to same ISP "and" your ISP requires you to run BGP or provides you your own AS number.

now regarding your question, when you say you are using HRSP "SNAT" and OSPF, i'm guessing that you only have on ISP, they assigned you your own public IP, but not AS number. You have redundant routers where you use SNAT as fail over mechanism.

So to make it short, I don't think BGP is applicable in your case as you only have one ISP connection and the complexity of BGP is necessary on your situation.

if you can advise why you wish to use BGP, then I can help you further in your clarifications.

We have two leased lines to two different sites (us) from two different sites (customer).